[v5.15] INFO: task hung in cgroup_can_fork (2)

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syzbot

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Sep 10, 2025, 11:23:30 PMSep 10

to syzkaller...@googlegroups.com

Hello,

syzbot found the following issue on:

HEAD commit: de9476bb4f1b Linux 5.15.192
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=128f5d62580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4aee9f779ad20a6a
dashboard link: https://syzkaller.appspot.com/bug?extid=6b5cbd79e0efb0612e59
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/932603ceec6d/disk-de9476bb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8532a10f4612/vmlinux-de9476bb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/74c54ec058f6/bzImage-de9476bb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6b5cbd...@syzkaller.appspotmail.com

INFO: task kthreadd:2 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kthreadd state:D stack:27304 pid: 2 ppid: 0 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
cgroup_css_set_fork kernel/cgroup/cgroup.c:6196 [inline]
cgroup_can_fork+0xc94/0xda0 kernel/cgroup/cgroup.c:6314
copy_process+0x2290/0x3e00 kernel/fork.c:2382
kernel_clone+0x219/0x930 kernel/fork.c:2679
kernel_thread+0xc8/0x120 kernel/fork.c:2731
create_kthread kernel/kthread.c:357 [inline]
kthreadd+0x520/0x6f0 kernel/kthread.c:703
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
INFO: task dhcpcd:3854 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:dhcpcd state:D stack:21376 pid: 3854 ppid: 3853 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
cgroup_css_set_fork kernel/cgroup/cgroup.c:6196 [inline]
cgroup_can_fork+0xc94/0xda0 kernel/cgroup/cgroup.c:6314
copy_process+0x2290/0x3e00 kernel/fork.c:2382
kernel_clone+0x219/0x930 kernel/fork.c:2679
__do_sys_clone kernel/fork.c:2796 [inline]
__se_sys_clone kernel/fork.c:2780 [inline]
__x64_sys_clone+0x170/0x1c0 kernel/fork.c:2780
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f13e9e6b636
RSP: 002b:00007ffc9d92aeb0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffc9d92aeb8 RCX: 00007f13e9e6b636
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffc9d94b400 R08: 0000000000000000 R09: 0000000000000001
R10: 00007f13e9d97a10 R11: 0000000000000246 R12: 00007ffc9d92aff0
R13: 0000000000000000 R14: 0000000000000000 R15: 000055a3c1391ac0
</TASK>
INFO: task syz-executor:4182 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:18344 pid: 4182 ppid: 4177 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
inode_lock_nested include/linux/fs.h:822 [inline]
filename_create+0x1f2/0x450 fs/namei.c:3835
do_mkdirat+0x9d/0x5a0 fs/namei.c:4080
__do_sys_mkdirat fs/namei.c:4105 [inline]
__se_sys_mkdirat fs/namei.c:4103 [inline]
__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f91a04e7417
RSP: 002b:00007ffd39713de8 EFLAGS: 00000206 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffd39713e40 RCX: 00007f91a04e7417
RDX: 00000000000001ff RSI: 00007ffd39713e40 RDI: 00000000ffffff9c
RBP: 0000000000000001 R08: 0000000000000017 R09: 00007ffd39713b37
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
</TASK>
INFO: task syz-executor:4183 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:21536 pid: 4183 ppid: 4179 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
mmap_write_lock include/linux/mmap_lock.h:71 [inline]
mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
cpuset_attach+0x330/0x5f0 kernel/cgroup/cpuset.c:2376
cgroup_migrate_execute+0x7eb/0x1010 kernel/cgroup/cgroup.c:2574
cgroup_attach_task+0x562/0x7e0 kernel/cgroup/cgroup.c:2869
__cgroup1_procs_write+0x2e5/0x3f0 kernel/cgroup/cgroup-v1.c:527
cgroup_file_write+0x2f7/0x630 kernel/cgroup/cgroup.c:3943
kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2172 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x712/0xd00 fs/read_write.c:594
ksys_write+0x14d/0x250 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fbef5b1065f
RSP: 002b:00007ffc8340d420 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fbef5b1065f
RDX: 0000000000000001 RSI: 00007ffc8340d470 RDI: 0000000000000003
RBP: 00007ffc8340d9e0 R08: 0000000000000000 R09: 00007ffc8340d277
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
R13: 00007ffc8340d470 R14: 00007ffc8340d9a0 R15: 00007ffc8340d9e0
</TASK>
INFO: task syz-executor:4189 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:20104 pid: 4189 ppid: 4181 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
inode_lock_nested include/linux/fs.h:822 [inline]
filename_create+0x1f2/0x450 fs/namei.c:3835
do_mkdirat+0x9d/0x5a0 fs/namei.c:4080
__do_sys_mkdirat fs/namei.c:4105 [inline]
__se_sys_mkdirat fs/namei.c:4103 [inline]
__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fdc73261417
RSP: 002b:00007ffe0ec0fe98 EFLAGS: 00000202 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffe0ec0fef0 RCX: 00007fdc73261417
RDX: 00000000000001ff RSI: 00007ffe0ec0fef0 RDI: 00000000ffffff9c
RBP: 0000000000000001 R08: 0000000000000017 R09: 00007ffe0ec0fbe7
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
</TASK>
INFO: task syz-executor:4196 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor state:D stack:19560 pid: 4196 ppid: 4178 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
cgroup_mkdir+0xaf/0xe60 kernel/cgroup/cgroup.c:5556
kernfs_iop_mkdir+0x24c/0x3d0 fs/kernfs/dir.c:1175
vfs_mkdir+0x387/0x570 fs/namei.c:4065
do_mkdirat+0x1d7/0x5a0 fs/namei.c:4090
__do_sys_mkdirat fs/namei.c:4105 [inline]
__se_sys_mkdirat fs/namei.c:4103 [inline]
__x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fce1806a417
RSP: 002b:00007ffec40a2668 EFLAGS: 00000202 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffec40a26c0 RCX: 00007fce1806a417
RDX: 00000000000001ff RSI: 00007ffec40a26c0 RDI: 00000000ffffff9c
RBP: 0000000000000001 R08: 0000000000000017 R09: 00007ffec40a23b7
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
</TASK>
INFO: task syz.3.6:4296 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.6 state:D stack:25800 pid: 4296 ppid: 4192 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830
do_group_exit+0x12e/0x300 kernel/exit.c:997
get_signal+0x6ca/0x12c0 kernel/signal.c:2900
arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe424cfebe3
RSP: 002b:00007ffcb9a9ed78 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: fffffffffffffffc RBX: 00007fe4237676c0 RCX: 00007fe424cfebe3
RDX: 0000000000000000 RSI: 0000000000021000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00000000ffffffff R09: 0000000000000000
R10: 0000000000020022 R11: 0000000000000246 R12: 00007ffcb9a9eed0
R13: ffffffffffffffc0 R14: 0000000000001000 R15: 0000000000000000
</TASK>
INFO: task syz.3.6:4297 blocked for more than 145 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.6 state:D stack:24072 pid: 4297 ppid: 4192 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830
do_group_exit+0x12e/0x300 kernel/exit.c:997
get_signal+0x6ca/0x12c0 kernel/signal.c:2900
arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe424cfeba9
RSP: 002b:00007fe422f660e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fe424f45fa8 RCX: 00007fe424cfeba9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fe424f45fa8
RBP: 00007fe424f45fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe424f46038 R14: 00007ffcb9a9ecf0 R15: 00007ffcb9a9edd8
</TASK>

Showing all locks held in the system:
1 lock held by kthreadd/2:
#0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382
1 lock held by khungtaskd/27:
#0: ffffffff8c11c460 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
no locks held by klogd/3550.
2 locks held by udevd/3561:
#0: ffffffff8c1a64f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mmap kernel/fork.c:503 [inline]
#0: ffffffff8c1a64f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1466 [inline]
#0: ffffffff8c1a64f0 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x21f/0x1380 kernel/fork.c:1518
#1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: dup_mmap kernel/fork.c:504 [inline]
#1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
#1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: copy_mm+0x238/0x1380 kernel/fork.c:1518
1 lock held by dhcpcd/3854:
#0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382
2 locks held by getty/3949:
#0: ffff88814cd64098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
1 lock held by udevd/4174:
#0: ffff888079fcf828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff888079fcf828 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0xf3/0x230 mm/mmap.c:2949
1 lock held by udevd/4176:
#0: ffff88807ab20128 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff88807ab20128 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0xf3/0x230 mm/mmap.c:2949
1 lock held by syz-executor/4180:
#0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
2 locks held by syz-executor/4182:
#0: ffff88807a7a6460 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:377
#1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
#1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: filename_create+0x1f2/0x450 fs/namei.c:3835
7 locks held by syz-executor/4183:
#0: ffff88807c782460 (sb_writers#11){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff88802b3a2488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffffffff8c141d08 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
#3: ffffffff8bfbabd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2388 [inline]
#3: ffffffff8bfbabd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_procs_write_start+0x17c/0x580 kernel/cgroup/cgroup.c:2898
#4: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2390 [inline]
#4: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_procs_write_start+0x192/0x580 kernel/cgroup/cgroup.c:2898
#5: ffffffff8c14f748 (cpuset_mutex){+.+.}-{3:3}, at: cpuset_attach+0xac/0x5f0 kernel/cgroup/cpuset.c:2348
#6: ffff88807b105c28 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
#6: ffff88807b105c28 (&mm->mmap_lock){++++}-{3:3}, at: mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
2 locks held by syz-executor/4189:
#0: ffff88807a7a6460 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:377
#1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
#1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: filename_create+0x1f2/0x450 fs/namei.c:3835
3 locks held by syz-executor/4196:
#0: ffff88807a7a6460 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:377
#1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
#1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: filename_create+0x1f2/0x450 fs/namei.c:3835
#2: ffffffff8c141d08 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
1 lock held by udevd/4198:
#0: ffff88807b106a28 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff88807b106a28 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0xf3/0x230 mm/mmap.c:2949
1 lock held by syz.3.6/4296:
#0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
1 lock held by syz.3.6/4297:
#0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe0f/0xe50 kernel/hung_task.c:369
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 9 Comm: kworker/u4:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: bat_events batadv_nc_worker
RIP: 0010:check_preemption_disabled+0x60/0x110 lib/smp_processor_id.c:19
Code: 00 48 3b 4c 24 08 0f 85 c4 00 00 00 48 83 c4 10 5b 41 5e 41 5f 5d c3 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 <74> cc 65 4c 8b 3d e6 70 59 76 41 f6 47 2f 04 74 0a 41 83 bf 10 04
RSP: 0018:ffffc90000ce7a88 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffff88813fed0000 RCX: 0000000080000000
RDX: 0000000000000000 RSI: ffffffff8a0b2420 RDI: ffffffff8a59a240
RBP: ffffc90000ce7bd0 R08: dffffc0000000000 R09: fffffbfff1ad31e6
R10: fffffbfff1ad31e6 R11: 1ffffffff1ad31e5 R12: 000000000000004f
R13: dffffc0000000000 R14: ffff88813fed0aec R15: 1ffff9200019cf64
FS: 0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcb9a9eff8 CR3: 000000007e117000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lockdep_recursion_inc kernel/locking/lockdep.c:431 [inline]
lock_release+0x156/0x870 kernel/locking/lockdep.c:5642
rcu_read_unlock include/linux/rcupdate.h:772 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:416 [inline]
batadv_nc_worker+0x25b/0x5c0 net/batman-adv/network-coding.c:723
process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

syzbot

unread,

Sep 23, 2025, 11:27:28 AM (3 days ago) Sep 23

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: 43bb85222e53 Linux 5.15.193
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14c684e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb

dashboard link: https://syzkaller.appspot.com/bug?extid=6b5cbd79e0efb0612e59
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=155ac142580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0bc183664ae8/disk-43bb8522.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0fc2f6618934/vmlinux-43bb8522.xz
kernel image: https://storage.googleapis.com/syzbot-assets/af70b3957f4c/bzImage-43bb8522.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6b5cbd...@syzkaller.appspotmail.com

INFO: task kthreadd:2 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:kthreadd state:D stack:27328 pid: 2 ppid: 0 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
cgroup_css_set_fork kernel/cgroup/cgroup.c:6196 [inline]
cgroup_can_fork+0xc94/0xda0 kernel/cgroup/cgroup.c:6314
copy_process+0x2290/0x3e00 kernel/fork.c:2382
kernel_clone+0x219/0x930 kernel/fork.c:2679
kernel_thread+0xc8/0x120 kernel/fork.c:2731
create_kthread kernel/kthread.c:357 [inline]
kthreadd+0x520/0x6f0 kernel/kthread.c:703
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>

INFO: task kworker/u4:0:9 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:kworker/u4:0 state:D stack:24960 pid: 9 ppid: 2 flags:0x00004000
Workqueue: events_unbound call_usermodehelper_exec_work

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
cgroup_css_set_fork kernel/cgroup/cgroup.c:6196 [inline]
cgroup_can_fork+0xc94/0xda0 kernel/cgroup/cgroup.c:6314
copy_process+0x2290/0x3e00 kernel/fork.c:2382
kernel_clone+0x219/0x930 kernel/fork.c:2679
kernel_thread+0xc8/0x120 kernel/fork.c:2731

call_usermodehelper_exec_sync kernel/umh.c:135 [inline]
call_usermodehelper_exec_work+0x93/0x220 kernel/umh.c:166

process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>

INFO: task kworker/u4:2:154 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:kworker/u4:2 state:D stack:24352 pid: 154 ppid: 2 flags:0x00004000
Workqueue: netns cleanup_net

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478

schedule_timeout+0x97/0x280 kernel/time/timer.c:1890
do_wait_for_common+0x29a/0x440 kernel/sched/completion.c:85
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x48/0x60 kernel/sched/completion.c:138
kthread_stop+0x16e/0x540 kernel/kthread.c:666
__netif_napi_del+0x685/0x7a0 net/core/dev.c:7055
netif_napi_del include/linux/netdevice.h:2547 [inline]
peer_remove_after_dead+0xe1/0x1a0 drivers/net/wireguard/peer.c:125
wg_peer_remove_all+0x447/0x4e0 drivers/net/wireguard/peer.c:184
wg_destruct+0x176/0x300 drivers/net/wireguard/device.c:238
netdev_run_todo+0x82d/0xa40 net/core/dev.c:10691
default_device_exit_batch+0x33b/0x390 net/core/dev.c:11668
ops_exit_list net/core/net_namespace.c:177 [inline]
cleanup_net+0x77b/0xb80 net/core/net_namespace.c:635

INFO: task udevd:4215 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:udevd state:D stack:26864 pid: 4215 ppid: 3562 flags:0x00004002

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]

exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830
do_group_exit+0x12e/0x300 kernel/exit.c:997

__do_sys_exit_group kernel/exit.c:1008 [inline]
__se_sys_exit_group kernel/exit.c:1006 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006

do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f1e79e6b6c5
RSP: 002b:00007ffffa5ad4e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000558757bb2fa0 RCX: 00007f1e79e6b6c5
RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000
RBP: 0000558757b9e910 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007ffffa5ad530 R14: 0000000000000000 R15: 0000000000000000
</TASK>
INFO: task udevd:4217 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:udevd state:D stack:27200 pid: 4217 ppid: 3562 flags:0x00004002

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]

exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830
do_group_exit+0x12e/0x300 kernel/exit.c:997

__do_sys_exit_group kernel/exit.c:1008 [inline]
__se_sys_exit_group kernel/exit.c:1006 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006

do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f1e79e6b6c5
RSP: 002b:00007ffffa5ad4e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000558757bc6a40 RCX: 00007f1e79e6b6c5
RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000
RBP: 0000558757b9e910 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007ffffa5ad530 R14: 0000000000000000 R15: 0000000000000000
</TASK>
INFO: task udevd:4247 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:udevd state:D stack:25536 pid: 4247 ppid: 3562 flags:0x00004002

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]

exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830
do_group_exit+0x12e/0x300 kernel/exit.c:997

__do_sys_exit_group kernel/exit.c:1008 [inline]
__se_sys_exit_group kernel/exit.c:1006 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006

do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f1e79e6b6c5
RSP: 002b:00007ffffa5ad4e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000558757bc14d0 RCX: 00007f1e79e6b6c5
RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000
RBP: 0000558757b9e910 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007ffffa5ad530 R14: 0000000000000000 R15: 0000000000000000
</TASK>
INFO: task napi/wg2-0:4291 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:napi/wg2-0 state:D stack:28896 pid: 4291 ppid: 2 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]

exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830

kthread_exit+0x11/0x20 kernel/kthread.c:283
kthread+0x454/0x520 kernel/kthread.c:336
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
INFO: task syz-executor:4330 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz-executor state:D stack:21984 pid: 4330 ppid: 4326 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639

__cgroup_procs_write+0x73/0x350 kernel/cgroup/cgroup.c:4989
cgroup_procs_write+0x23/0x40 kernel/cgroup/cgroup.c:5029

cgroup_file_write+0x2f7/0x630 kernel/cgroup/cgroup.c:3943
kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2172 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x712/0xd00 fs/read_write.c:594
ksys_write+0x14d/0x250 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f0c5589197f
RSP: 002b:00007ffd619fb190 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f0c5589197f
RDX: 0000000000000001 RSI: 00007ffd619fb1e0 RDI: 0000000000000003
RBP: 00007ffd619fb750 R08: 0000000000000000 R09: 00007ffd619fafe7

R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001

R13: 00007ffd619fb1e0 R14: 00007ffd619fb710 R15: 00007ffd619fb750
</TASK>
INFO: task syz-executor:4333 blocked for more than 145 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz-executor state:D stack:21856 pid: 4333 ppid: 4329 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
mmap_write_lock include/linux/mmap_lock.h:71 [inline]
mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
cpuset_attach+0x330/0x5f0 kernel/cgroup/cpuset.c:2376
cgroup_migrate_execute+0x7eb/0x1010 kernel/cgroup/cgroup.c:2574
cgroup_attach_task+0x562/0x7e0 kernel/cgroup/cgroup.c:2869
__cgroup1_procs_write+0x2e5/0x3f0 kernel/cgroup/cgroup-v1.c:527
cgroup_file_write+0x2f7/0x630 kernel/cgroup/cgroup.c:3943
kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2172 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x712/0xd00 fs/read_write.c:594
ksys_write+0x14d/0x250 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f7ea1ee097f
RSP: 002b:00007ffc7820d1d0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f7ea1ee097f
RDX: 0000000000000001 RSI: 00007ffc7820d220 RDI: 0000000000000003
RBP: 00007ffc7820d790 R08: 0000000000000000 R09: 00007ffc7820d027

R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001

R13: 00007ffc7820d220 R14: 00007ffc7820d750 R15: 00007ffc7820d790
</TASK>
INFO: task udevd:4373 blocked for more than 145 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:udevd state:D stack:27104 pid: 4373 ppid: 3562 flags:0x00004002

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]

exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830
do_group_exit+0x12e/0x300 kernel/exit.c:997

__do_sys_exit_group kernel/exit.c:1008 [inline]
__se_sys_exit_group kernel/exit.c:1006 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006

do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f1e79e6b6c5
RSP: 002b:00007ffffa5ad4e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000558757bb11a0 RCX: 00007f1e79e6b6c5
RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000
RBP: 0000558757b9e910 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007ffffa5ad530 R14: 0000000000000000 R15: 0000000000000000

</TASK>

Showing all locks held in the system:
1 lock held by kthreadd/2:

#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382
3 locks held by kworker/u4:0/9:
#0: ffff888016879138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90000ce7d00 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382

1 lock held by khungtaskd/27:

#0: ffffffff8c11c660 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
4 locks held by kworker/u4:2/154:
#0: ffff8880169cd938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90001e47d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8d22c3d0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x132/0xb80 net/core/net_namespace.c:589
#3: ffff8880575793e8 (&wg->device_update_lock){+.+.}-{3:3}, at: wg_destruct+0x112/0x300 drivers/net/wireguard/device.c:233
1 lock held by dhcpcd/3855:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382
2 locks held by getty/3952:
#0: ffff88814c973098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc900021ce2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
1 lock held by udevd/4215:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
1 lock held by udevd/4217:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
1 lock held by udevd/4247:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
1 lock held by napi/wg2-0/4291:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
1 lock held by syz-executor/4325:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
2 locks held by syz-executor/4327:
#0: ffffffff8c1a66f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mmap kernel/fork.c:503 [inline]
#0: ffffffff8c1a66f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1466 [inline]
#0: ffffffff8c1a66f0 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x21f/0x1380 kernel/fork.c:1518
#1: ffff88807e718828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#1: ffff88807e718828 (&mm->mmap_lock){++++}-{3:3}, at: dup_mmap kernel/fork.c:504 [inline]
#1: ffff88807e718828 (&mm->mmap_lock){++++}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
#1: ffff88807e718828 (&mm->mmap_lock){++++}-{3:3}, at: copy_mm+0x238/0x1380 kernel/fork.c:1518
3 locks held by syz-executor/4330:
#0: ffff88801a39c460 (sb_writers#10){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff888079943c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffffffff8c141f08 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
7 locks held by syz-executor/4333:
#0: ffff88807b4e0460 (sb_writers#11){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff88805c391888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffffffff8c141f08 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
#3: ffffffff8bfbadd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2388 [inline]
#3: ffffffff8bfbadd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_procs_write_start+0x17c/0x580 kernel/cgroup/cgroup.c:2898
#4: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2390 [inline]
#4: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_procs_write_start+0x192/0x580 kernel/cgroup/cgroup.c:2898
#5: ffffffff8c14f948 (cpuset_mutex){+.+.}-{3:3}, at: cpuset_attach+0xac/0x5f0 kernel/cgroup/cpuset.c:2348
#6: ffff88807e71f128 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
#6: ffff88807e71f128 (&mm->mmap_lock){++++}-{3:3}, at: mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
1 lock held by udevd/4373:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
3 locks held by kworker/u4:6/4422:
#0: ffff888016879138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc9000386fd00 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025

Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe0f/0xe50 kernel/hung_task.c:369
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>

Sending NMI from CPU 1 to CPUs 0:

NMI backtrace for cpu 0

CPU: 0 PID: 1451 Comm: kworker/u4:5 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: phy10 ieee80211_iface_work
RIP: 0010:check_kcov_mode kernel/kcov.c:183 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x32/0x60 kernel/kcov.c:206
Code: 94 a4 8a 7e 65 8b 15 95 a4 8a 7e 81 e2 00 01 ff 00 74 11 81 fa 00 01 00 00 75 35 83 b9 34 16 00 00 00 74 2c 8b 91 10 16 00 00 <83> fa 02 75 21 48 8b 91 18 16 00 00 48 8b 32 48 8d 7e 01 8b 89 14
RSP: 0018:ffffc900051978f0 EFLAGS: 00000246
RAX: ffffffff893f70b2 RBX: 0000000000000002 RCX: ffff888023730000
RDX: 0000000000000000 RSI: 00000000000001e0 RDI: 0000000000000037
RBP: 0000000000000037 R08: dffffc0000000000 R09: fffffbfff1ad323e
R10: fffffbfff1ad323e R11: 1ffffffff1ad323d R12: 000000000000000b
R13: 00000000000001e0 R14: dffffc0000000000 R15: ffff88805d3cb350
FS: 0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000558757bac270 CR3: 000000002a3f1000 CR4: 00000000003506f0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>

ieee80211_sta_get_rates+0x422/0x6b0 net/mac80211/util.c:2137
ieee80211_update_sta_info net/mac80211/ibss.c:1007 [inline]
ieee80211_rx_bss_info net/mac80211/ibss.c:1121 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1614 [inline]
ieee80211_ibss_rx_queued_mgmt+0xf47/0x29c0 net/mac80211/ibss.c:1643
ieee80211_iface_process_skb net/mac80211/iface.c:1459 [inline]
ieee80211_iface_work+0x70e/0xc60 net/mac80211/iface.c:1513

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

syzbot

unread,

Sep 23, 2025, 11:45:35 AM (3 days ago) Sep 23

to syzkaller...@googlegroups.com

Hello,

syzbot found the following issue on:

HEAD commit: 363a599da6d9 Linux 6.1.153
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1683627c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7eb38bd5021fec61
dashboard link: https://syzkaller.appspot.com/bug?extid=80596b0b7c6cb3fdc803

compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1286c142580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1183627c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7cf87f25c694/disk-363a599d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ec86135ba3cc/vmlinux-363a599d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/117cec1ae5fa/bzImage-363a599d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+80596b...@syzkaller.appspotmail.com

INFO: task syz-executor:4398 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz-executor state:D stack:22272 pid:4398 ppid:4393 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
percpu_rwsem_wait+0x2bd/0x300 kernel/locking/percpu-rwsem.c:162
__percpu_down_read+0xda/0x120 kernel/locking/percpu-rwsem.c:177
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:748 [inline]
cgroup_css_set_fork kernel/cgroup/cgroup.c:6403 [inline]
cgroup_can_fork+0xc27/0xd30 kernel/cgroup/cgroup.c:6536
copy_process+0x248b/0x4020 kernel/fork.c:2446
kernel_clone+0x225/0x8b0 kernel/fork.c:2757
__do_sys_clone kernel/fork.c:2898 [inline]
__se_sys_clone kernel/fork.c:2882 [inline]
__x64_sys_clone+0x17c/0x1d0 kernel/fork.c:2882
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fcb54385613
RSP: 002b:00007ffc9688df18 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fcb54385613

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011

RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 00005555849087d0 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000000927c0 R14: 000000000001e7ae R15: 00007ffc9688e0b0
</TASK>
INFO: task syz-executor:4403 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz-executor state:D stack:21480 pid:4403 ppid:4394 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
rwsem_down_write_slowpath+0xbed/0x1090 kernel/locking/rwsem.c:1189
mmap_write_lock include/linux/mmap_lock.h:71 [inline]
mpol_rebind_mm+0xbe/0x370 mm/mempolicy.c:386
cpuset_attach+0x284/0x540 kernel/cgroup/cpuset.c:2663
cgroup_migrate_execute+0x7a3/0xf30 kernel/cgroup/cgroup.c:2639
cgroup_attach_task+0x558/0x840 kernel/cgroup/cgroup.c:2930
__cgroup1_procs_write+0x2e0/0x3e0 kernel/cgroup/cgroup-v1.c:522
cgroup_file_write+0x2f8/0x660 kernel/cgroup/cgroup.c:4077
kernfs_fop_write_iter+0x3b2/0x520 fs/kernfs/file.c:352
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x44c/0x960 fs/read_write.c:584
ksys_write+0x143/0x240 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f98b278d97f
RSP: 002b:00007ffce6918290 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f98b278d97f
RDX: 0000000000000001 RSI: 00007ffce69182e0 RDI: 0000000000000003
RBP: 00007ffce6918850 R08: 0000000000000000 R09: 00007ffce69180e7

R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001

R13: 00007ffce69182e0 R14: 00007ffce6918810 R15: 00007ffce6918850
</TASK>
INFO: task syz.2.27:4465 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.2.27 state:D stack:25320 pid:4465 ppid:4401 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
rwsem_down_write_slowpath+0xbed/0x1090 kernel/locking/rwsem.c:1189
mmap_write_lock include/linux/mmap_lock.h:71 [inline]
exit_mmap+0x20f/0x8e0 mm/mmap.c:3258
__mmput+0x118/0x3c0 kernel/fork.c:1200
exit_mm+0x1e6/0x2c0 kernel/exit.c:565
do_exit+0x8c1/0x2400 kernel/exit.c:867
do_group_exit+0x217/0x2d0 kernel/exit.c:1022
__do_sys_exit_group kernel/exit.c:1033 [inline]
__se_sys_exit_group kernel/exit.c:1031 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1031
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f70e578eec9
RSP: 002b:00007ffeba568a98 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f70e578eec9
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffeba568afc R08: 00000005ba568b8f R09: 00000000000927c0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000002
R13: 00000000000927c0 R14: 000000000001d15c R15: 00007ffeba568b50
</TASK>
INFO: task syz.1.18:4524 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.1.18 state:D stack:25696 pid:4524 ppid:4390 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5244 [inline]
__schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
schedule+0xb9/0x180 kernel/sched/core.c:6637
rwsem_down_write_slowpath+0xbed/0x1090 kernel/locking/rwsem.c:1189
mmap_write_lock include/linux/mmap_lock.h:71 [inline]
exit_mmap+0x20f/0x8e0 mm/mmap.c:3258
__mmput+0x118/0x3c0 kernel/fork.c:1200
exit_mm+0x1e6/0x2c0 kernel/exit.c:565
do_exit+0x8c1/0x2400 kernel/exit.c:867
do_group_exit+0x217/0x2d0 kernel/exit.c:1022
__do_sys_exit_group kernel/exit.c:1033 [inline]
__se_sys_exit_group kernel/exit.c:1031 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1031
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fce19f8eec9
RSP: 002b:00007ffe87a9fab8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fce19f8eec9
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: 0000000587a9fbaf R09: 00007fce1a1b1280
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fce1a1b1280 R14: 0000000000000003 R15: 00007ffe87a9fb70

</TASK>

Showing all locks held in the system:

1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8cb2b570 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8cb2bd90 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
#0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8cb2abe0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
2 locks held by getty/4029:
#0: ffff88807e5d8098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41b/0x1380 drivers/tty/n_tty.c:2198
1 lock held by udevd/4289:
#0: ffffffff8cb53810 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x578/0x2400 kernel/exit.c:827
1 lock held by udevd/4295:
#0: ffff88801e3297d8 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff88801e3297d8 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0x141/0x290 mm/mmap.c:2933
1 lock held by syz-executor/4387:
#0: ffffffff8cb53810 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x578/0x2400 kernel/exit.c:827
2 locks held by syz-executor/4389:
#0: ffffffff8cbc4e50 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mmap kernel/fork.c:593 [inline]
#0: ffffffff8cbc4e50 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1541 [inline]
#0: ffffffff8cbc4e50 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x2a9/0x15c0 kernel/fork.c:1590
#1: ffff88807bf4b5d8 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#1: ffff88807bf4b5d8 (&mm->mmap_lock){++++}-{3:3}, at: dup_mmap kernel/fork.c:594 [inline]
#1: ffff88807bf4b5d8 (&mm->mmap_lock){++++}-{3:3}, at: dup_mm kernel/fork.c:1541 [inline]
#1: ffff88807bf4b5d8 (&mm->mmap_lock){++++}-{3:3}, at: copy_mm+0x2c3/0x15c0 kernel/fork.c:1590
1 lock held by syz-executor/4398:
#0: ffffffff8cb53810 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x248b/0x4020 kernel/fork.c:2446
7 locks held by syz-executor/4403:
#0: ffff8880239c8460 (sb_writers#11){.+.+}-{0:0}, at: vfs_write+0x256/0x960 fs/read_write.c:580
#1: ffff888069ecf488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e3/0x520 fs/kernfs/file.c:343
#2: ffffffff8cb53628 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock include/linux/cgroup.h:442 [inline]
#2: ffffffff8cb53628 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1677
#3: ffffffff8c9c7a70 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2453 [inline]
#3: ffffffff8c9c7a70 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_procs_write_start+0x183/0x600 kernel/cgroup/cgroup.c:2959
#4: ffffffff8cb53810 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2455 [inline]
#4: ffffffff8cb53810 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_procs_write_start+0x199/0x600 kernel/cgroup/cgroup.c:2959
#5: ffffffff8cb61ba8 (cpuset_mutex){+.+.}-{3:3}, at: cpuset_attach+0xac/0x540 kernel/cgroup/cpuset.c:2647
#6: ffff88807bf4bd58 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
#6: ffff88807bf4bd58 (&mm->mmap_lock){++++}-{3:3}, at: mpol_rebind_mm+0xbe/0x370 mm/mempolicy.c:386
1 lock held by dhcpcd-run-hook/4464:
#0: ffff888078f562d8 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
#0: ffff888078f562d8 (&mm->mmap_lock){++++}-{3:3}, at: vm_mmap_pgoff+0x15d/0x2b0 mm/util.c:518
1 lock held by syz.2.27/4465:
#0: ffff888078f57958 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
#0: ffff888078f57958 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x20f/0x8e0 mm/mmap.c:3258
1 lock held by syz.1.18/4524:
#0: ffff88807fbe62d8 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
#0: ffff88807fbe62d8 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x20f/0x8e0 mm/mmap.c:3258

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<TASK>

dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3f4/0x470 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xeee/0xf30 kernel/hung_task.c:377
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Sending NMI from CPU 0 to CPUs 1:

NMI backtrace for cpu 1

CPU: 1 PID: 61 Comm: kworker/u4:4 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025

Workqueue: phy8 ieee80211_iface_work
RIP: 0010:lock_release+0x77/0x910 kernel/locking/lockdep.c:5670
Code: 41 8c 48 c7 44 24 70 80 73 63 81 4c 8d 7c 24 60 49 c1 ef 03 48 b8 f1 f1 f1 f1 00 f2 f2 f2 4b 89 04 2f 66 43 c7 44 2f 09 f3 f3 <43> c6 44 2f 0b f3 0f 1f 44 00 00 65 8b 1d 97 a5 9e 7e 48 c7 c0 f0
RSP: 0018:ffffc90001577040 EFLAGS: 00000806
RAX: f2f2f200f1f1f1f1 RBX: 0000000000000a02 RCX: dffffc0000000000
RDX: 0000000000000001 RSI: ffffffff816b36bb RDI: ffffffff96e8f430
RBP: ffffc90001577150 R08: 0000000000000004 R09: 0000000000000003
R10: fffff520002aee10 R11: 1ffff920002aee10 R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff96e8f418 R15: 1ffff920002aee14
FS: 0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007fcdff052700 CR3: 000000000c88e000 CR4: 00000000003506e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>

__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:149 [inline]
_raw_spin_unlock_irqrestore+0x6d/0x100 kernel/locking/spinlock.c:194
debug_rcu_head_queue kernel/rcu/rcu.h:191 [inline]
kvfree_call_rcu+0xcb/0x870 kernel/rcu/tree.c:3396
cfg80211_update_known_bss+0x178/0xa20 net/wireless/scan.c:-1
cfg80211_bss_update+0x15f/0x2250 net/wireless/scan.c:1853
cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2512 [inline]
cfg80211_inform_bss_frame_data+0x9f4/0x1370 net/wireless/scan.c:2545
ieee80211_bss_info_update+0x734/0xbc0 net/mac80211/scan.c:190
ieee80211_rx_bss_info net/mac80211/ibss.c:1120 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1609 [inline]
ieee80211_ibss_rx_queued_mgmt+0x17b4/0x2b10 net/mac80211/ibss.c:1638
ieee80211_iface_process_skb net/mac80211/iface.c:1671 [inline]
ieee80211_iface_work+0x726/0xc80 net/mac80211/iface.c:1725
process_one_work+0x898/0x1160 kernel/workqueue.c:2292
worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

</TASK>

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

syzbot

unread,

Sep 23, 2025, 11:51:32 PM (3 days ago) Sep 23

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: 43bb85222e53 Linux 5.15.193
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=12e18d34580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb

dashboard link: https://syzkaller.appspot.com/bug?extid=6b5cbd79e0efb0612e59
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=150e8f12580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1547e27c580000

Downloadable assets:

disk image: https://storage.googleapis.com/syzbot-assets/0bc183664ae8/disk-43bb8522.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0fc2f6618934/vmlinux-43bb8522.xz
kernel image: https://storage.googleapis.com/syzbot-assets/af70b3957f4c/bzImage-43bb8522.xz

task:kthreadd state:D stack:27232 pid: 2 ppid: 0 flags:0x00004000

INFO: task kworker/0:0:7 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:kworker/0:0 state:D stack:25768 pid: 7 ppid: 2 flags:0x00004000
Workqueue: ipv6_addrconf addrconf_dad_work

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743

addrconf_dad_work+0xc4/0x1520 net/ipv6/addrconf.c:4110

INFO: task kworker/u4:1:144 blocked for more than 143 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:kworker/u4:1 state:D stack:21128 pid: 144 ppid: 2 flags:0x00004000
Workqueue: netns cleanup_net

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743

tc_action_net_exit include/net/act_api.h:155 [inline]
gate_exit_net+0x2c/0x100 net/sched/act_gate.c:624

ops_exit_list net/core/net_namespace.c:177 [inline]
cleanup_net+0x77b/0xb80 net/core/net_namespace.c:635

INFO: task udevd:3561 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:udevd state:D stack:24488 pid: 3561 ppid: 1 flags:0x00004002

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478

schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743

device_lock include/linux/device.h:760 [inline]
uevent_show+0x17a/0x330 drivers/base/core.c:2408
dev_attr_show+0x50/0xb0 drivers/base/core.c:2110
sysfs_kf_seq_show+0x316/0x4c0 fs/sysfs/file.c:61
seq_read_iter+0x49b/0xd50 fs/seq_file.c:230
call_read_iter include/linux/fs.h:2166 [inline]
new_sync_read fs/read_write.c:404 [inline]
vfs_read+0x725/0xcf0 fs/read_write.c:485
ksys_read+0x14d/0x250 fs/read_write.c:623

do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f4cfd344407
RSP: 002b:00007ffd1f21bc80 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f4cfd256880 RCX: 00007f4cfd344407
RDX: 0000000000001000 RSI: 000055d6c6ae2f10 RDI: 000000000000000c
RBP: 00007f4cfd48cff0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000000000000000a
R13: 00007f4cfd48cea0 R14: 0000000000000000 R15: 000055d6c6ad07a0
</TASK>
INFO: task kworker/1:21:4312 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:kworker/1:21 state:D stack:24736 pid: 4312 ppid: 2 flags:0x00004000
Workqueue: ipv6_addrconf addrconf_dad_work

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743

addrconf_dad_work+0xc4/0x1520 net/ipv6/addrconf.c:4110

INFO: task syz-executor:4324 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz-executor state:D stack:22528 pid: 4324 ppid: 4318 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743

new_device_store+0x13c/0x740 drivers/net/netdevsim/bus.c:295

kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2172 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x712/0xd00 fs/read_write.c:594
ksys_write+0x14d/0x250 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f7df6af897f
RSP: 002b:00007fff0f5d2630 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f7df6af897f
RDX: 0000000000000003 RSI: 00007fff0f5d2680 RDI: 0000000000000005
RBP: 00007f7df6b7e25d R08: 0000000000000000 R09: 00007fff0f5d2487
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 00007fff0f5d2680 R14: 00007f7df787f620 R15: 0000000000000003
</TASK>
INFO: task syz-executor:4330 blocked for more than 144 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz-executor state:D stack:21768 pid: 4330 ppid: 4322 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
mmap_write_lock include/linux/mmap_lock.h:71 [inline]
mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
cpuset_attach+0x330/0x5f0 kernel/cgroup/cpuset.c:2376
cgroup_migrate_execute+0x7eb/0x1010 kernel/cgroup/cgroup.c:2574
cgroup_attach_task+0x562/0x7e0 kernel/cgroup/cgroup.c:2869
__cgroup1_procs_write+0x2e5/0x3f0 kernel/cgroup/cgroup-v1.c:527
cgroup_file_write+0x2f7/0x630 kernel/cgroup/cgroup.c:3943
kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
call_write_iter include/linux/fs.h:2172 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x712/0xd00 fs/read_write.c:594
ksys_write+0x14d/0x250 fs/read_write.c:647
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f496554c97f
RSP: 002b:00007ffcd6804390 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f496554c97f
RDX: 0000000000000001 RSI: 00007ffcd68043e0 RDI: 0000000000000003
RBP: 00007ffcd6804950 R08: 0000000000000000 R09: 00007ffcd68041e7

R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001

R13: 00007ffcd68043e0 R14: 00007ffcd6804910 R15: 00007ffcd6804950
</TASK>
INFO: task syz-executor:4332 blocked for more than 145 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz-executor state:D stack:21832 pid: 4332 ppid: 4325 flags:0x00004000

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743

devlink_nl_port_fill+0x295/0x870 net/core/devlink.c:995
devlink_port_notify+0x4c/0x170 net/core/devlink.c:1052
devlink_port_register+0x446/0x4b0 net/core/devlink.c:9127
__nsim_dev_port_add+0x2cf/0x980 drivers/net/netdevsim/dev.c:1303
nsim_dev_port_add_all+0x37/0x100 drivers/net/netdevsim/dev.c:1372
nsim_dev_probe+0x754/0x9c0 drivers/net/netdevsim/dev.c:1513
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x284/0xc80 drivers/base/dd.c:595
__driver_probe_device+0x18c/0x330 drivers/base/dd.c:755
driver_probe_device+0x4f/0x420 drivers/base/dd.c:785
__device_attach_driver+0x2b0/0x500 drivers/base/dd.c:907
bus_for_each_drv+0x175/0x200 drivers/base/bus.c:429
__device_attach+0x29b/0x460 drivers/base/dd.c:979
bus_probe_device+0xbc/0x1e0 drivers/base/bus.c:489
device_add+0xa00/0xfb0 drivers/base/core.c:3412
nsim_bus_dev_new drivers/net/netdevsim/bus.c:435 [inline]
new_device_store+0x3d8/0x740 drivers/net/netdevsim/bus.c:302

RIP: 0033:0x7fe36763e97f
RSP: 002b:00007ffcf16fd170 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007fe36763e97f
RDX: 0000000000000003 RSI: 00007ffcf16fd1c0 RDI: 0000000000000005
RBP: 00007fe3676c425d R08: 0000000000000000 R09: 00007ffcf16fcfc7
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 00007ffcf16fd1c0 R14: 00007fe3683c5620 R15: 0000000000000003
</TASK>
INFO: task syz.2.22:4383 blocked for more than 145 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:syz.2.22 state:D stack:24512 pid: 4383 ppid: 4323 flags:0x00004004

Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
__percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
exit_signals+0x3e5/0x510 kernel/signal.c:2991
do_exit+0x256/0x20a0 kernel/exit.c:830
do_group_exit+0x12e/0x300 kernel/exit.c:997

__do_sys_exit_group kernel/exit.c:1008 [inline]
__se_sys_exit_group kernel/exit.c:1006 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1006

do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

RIP: 0033:0x7f6dc997bec9
RSP: 002b:00007ffcd5e3b358 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f6dc997bec9

RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000

RBP: 00007ffcd5e3b3bc R08: 00000005d5e3b44f R09: 00000000000927c0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 0000000000023278 R15: 00007ffcd5e3b410

</TASK>

Showing all locks held in the system:
1 lock held by kthreadd/2:

#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382
3 locks held by kworker/0:0/7:
#0: ffff88802a9e3538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc90000cc7d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8d238048 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x1520 net/ipv6/addrconf.c:4110

1 lock held by khungtaskd/27:

#0: ffffffff8c11c660 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30

4 locks held by kworker/u4:1/144:
#0: ffff8880169cd938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc900016cfd00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8d22c3d0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x132/0xb80 net/core/net_namespace.c:589
#3: ffffffff8d238048 (rtnl_mutex){+.+.}-{3:3}, at: tc_action_net_exit include/net/act_api.h:155 [inline]
#3: ffffffff8d238048 (rtnl_mutex){+.+.}-{3:3}, at: gate_exit_net+0x2c/0x100 net/sched/act_gate.c:624
3 locks held by kworker/0:3/1324:
#0: ffff888016871938 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc9000547fd00 ((reg_check_chans).work){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8d238048 (rtnl_mutex){+.+.}-{3:3}, at: reg_check_chans_work+0x81/0xa50 net/wireless/reg.c:2437
4 locks held by udevd/3561:
#0: ffff8880757c2c30 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xad/0xd50 fs/seq_file.c:182
#1: ffff8880248ed488 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x51/0x3c0 fs/kernfs/file.c:112
#2: ffff888059b8a3a8 (kn->active#32){++++}-{0:0}, at: kernfs_seq_start+0x71/0x3c0 fs/kernfs/file.c:113
#3: ffff888076dd1178 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#3: ffff888076dd1178 (&dev->mutex){....}-{3:3}, at: uevent_show+0x17a/0x330 drivers/base/core.c:2408

1 lock held by dhcpcd/3854:

#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382

2 locks held by getty/3949:

#0: ffff88802b95f098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc900021ce2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
3 locks held by kworker/1:21/4312:
#0: ffff88802a9e3538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
#1: ffffc900031bfd00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
#2: ffffffff8d238048 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x1520 net/ipv6/addrconf.c:4110
1 lock held by syz-executor/4319:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
4 locks held by syz-executor/4320:
#0: ffffffff8d294cd0 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:802
#1: ffffffff8d294b28 (genl_mutex){+.+.}-{3:3}, at: genl_lock net/netlink/genetlink.c:33 [inline]
#1: ffffffff8d294b28 (genl_mutex){+.+.}-{3:3}, at: genl_rcv_msg+0x137/0xf40 net/netlink/genetlink.c:790
#2: ffffffff8d238048 (rtnl_mutex){+.+.}-{3:3}, at: wg_set_device+0xf2/0x1e70 drivers/net/wireguard/netlink.c:504
#3: ffff88807ee3d3e8 (&wg->device_update_lock){+.+.}-{3:3}, at: wg_set_device+0x10a/0x1e70 drivers/net/wireguard/netlink.c:505
4 locks held by syz-executor/4324:
#0: ffff88807ed4a460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff88805bde3088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffff888022b76ae8 (kn->active#363){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
#3: ffffffff8cb71d48 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: new_device_store+0x13c/0x740 drivers/net/netdevsim/bus.c:295
7 locks held by syz-executor/4330:
#0: ffff88807c17a460 (sb_writers#11){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff888079130c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffffffff8c141f08 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
#3: ffffffff8bfbadd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2388 [inline]
#3: ffffffff8bfbadd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_procs_write_start+0x17c/0x580 kernel/cgroup/cgroup.c:2898
#4: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2390 [inline]
#4: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_procs_write_start+0x192/0x580 kernel/cgroup/cgroup.c:2898
#5: ffffffff8c14f948 (cpuset_mutex){+.+.}-{3:3}, at: cpuset_attach+0xac/0x5f0 kernel/cgroup/cpuset.c:2348
#6: ffff888022ab8828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
#6: ffff888022ab8828 (&mm->mmap_lock){++++}-{3:3}, at: mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
6 locks held by syz-executor/4332:
#0: ffff88807ed4a460 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
#1: ffff88805bde2c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
#2: ffff888022b76ae8 (kn->active#363){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x208/0x4c0 fs/kernfs/file.c:288
#3: ffffffff8cb71d48 (nsim_bus_dev_list_lock){+.+.}-{3:3}, at: new_device_store+0x13c/0x740 drivers/net/netdevsim/bus.c:295
#4: ffff888076dd1178 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:760 [inline]
#4: ffff888076dd1178 (&dev->mutex){....}-{3:3}, at: __device_attach+0x85/0x460 drivers/base/dd.c:954
#5: ffffffff8d238048 (rtnl_mutex){+.+.}-{3:3}, at: devlink_nl_port_fill+0x295/0x870 net/core/devlink.c:995
2 locks held by kworker/u4:6/4373:
#0: ffff8880b913a358 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475
#1: ffff8880b9127888 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x495/0x810 kernel/sched/psi.c:882
1 lock held by syz.2.22/4383:
#0: ffffffff8c1420f0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025

NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0xb/0x10 arch/x86/kernel/process.c:729

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