[v6.6] INFO: task hung in ipmr_net_exit_batch

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: da47cbc25466 Linux 6.6.144
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15a0c589580000
kernel config: https://syzkaller.appspot.com/x/.config?x=938110aa66424b94
dashboard link: https://syzkaller.appspot.com/bug?extid=63d216e0795f467387ff
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f9357b0848a4/disk-da47cbc2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0d72e4376571/vmlinux-da47cbc2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/69ce7d2e1989/bzImage-da47cbc2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+63d216...@syzkaller.appspotmail.com

INFO: task kworker/u4:21:18856 blocked for more than 157 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u4:21 state:D stack:22096 pid:18856 ppid:2 flags:0x00004000
Workqueue: netns cleanup_net
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6833
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
ipmr_net_exit_batch+0x20/0x90 net/ipv4/ipmr.c:3144
ops_exit_list net/core/net_namespace.c:178 [inline]
cleanup_net+0x792/0xbb0 net/core/net_namespace.c:652
process_one_work kernel/workqueue.c:2653 [inline]
process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2730
worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2811
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
INFO: task syz.4.5123:23100 blocked for more than 160 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.5123 state:D stack:26824 pid:23100 ppid:22814 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x15ae/0x4660 kernel/sched/core.c:6700
schedule+0xbd/0x170 kernel/sched/core.c:6774
schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6833
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
rtnl_lock net/core/rtnetlink.c:78 [inline]
rtnetlink_rcv_msg+0x7ed/0xf90 net/core/rtnetlink.c:6473
netlink_rcv_skb+0x235/0x4c0 net/netlink/af_netlink.c:2550
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x7b1/0x930 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8d0/0xbf0 net/netlink/af_netlink.c:1899
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg net/socket.c:745 [inline]
____sys_sendmsg+0x61b/0x980 net/socket.c:2595
___sys_sendmsg+0x2a6/0x360 net/socket.c:2649
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2687 [inline]
__se_sys_sendmsg+0x1d0/0x2c0 net/socket.c:2685
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb452d9de59
RSP: 002b:00007fb453c59028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb453026270 RCX: 00007fb452d9de59
RDX: 0000000000098010 RSI: 0000200000000240 RDI: 0000000000000007
RBP: 00007fb452e33e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb453026308 R14: 00007fb453026270 R15: 00007ffdd608ffa8
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
#0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
3 locks held by udevd/5140:
1 lock held by dhcpcd/5436:
2 locks held by getty/5530:
#0: ffff88814c3ce0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
3 locks held by kworker/1:3/17434:
4 locks held by kworker/u4:21/18856:
#0: ffff88801a25c938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#0: ffff88801a25c938 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
#1: ffffc9000f88fd00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#1: ffffc9000f88fd00 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
#2: ffffffff8e3c8b10 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x14c/0xbb0 net/core/net_namespace.c:606
#3: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
#3: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3da/0x880 kernel/rcu/tree_exp.h:1004
2 locks held by kworker/1:6/22849:
#0: ffff888017c72538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#0: ffff888017c72538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
#1: ffffc9000b4dfd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#1: ffffc9000b4dfd00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
2 locks held by syz.5.5116/23053:
#0: ffffffff8e3c8b10 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x342/0x5d0 net/core/net_namespace.c:516
#1: ffffffff8d137640 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0x4c/0x530 kernel/rcu/tree.c:4089
1 lock held by syz.7.5120/23078:
#0: ffffffff8e3c8b10 (pernet_ops_rwsem){++++}-{3:3}, at: copy_net_ns+0x342/0x5d0 net/core/net_namespace.c:516
5 locks held by kworker/u5:2/23107:
#0: ffff88803143a538 ((wq_completion)hci2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#0: ffff88803143a538 ((wq_completion)hci2){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
#1: ffffc900039a7d00 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2628 [inline]
#1: ffffc900039a7d00 ((work_completion)(&hdev->cmd_sync_work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2730
#2: ffff888065f54e70 (&hdev->req_lock){+.+.}-{3:3}, at: hci_cmd_sync_work+0x1cc/0x380 net/bluetooth/hci_sync.c:332
#3: ffff888065f540b8 (&hdev->lock){+.+.}-{3:3}, at: hci_abort_conn_sync+0x98a/0xec0 net/bluetooth/hci_sync.c:5678
#4: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
#4: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3da/0x880 kernel/rcu/tree_exp.h:1004
1 lock held by dhcpcd/23118:
#0: ffff888048c12130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1780 [inline]
#0: ffff888048c12130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3264
1 lock held by dhcpcd/23119:
#0: ffff888048c10130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1780 [inline]
#0: ffff888048c10130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3264
1 lock held by dhcpcd/23120:
#0: ffff888048f50130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1780 [inline]
#0: ffff888048f50130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3264
1 lock held by dhcpcd/23121:
#0: ffff888048f52130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1780 [inline]
#0: ffff888048f52130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3264
1 lock held by dhcpcd/23124:
#0: ffff888048e64130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1780 [inline]
#0: ffff888048e64130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3264
1 lock held by dhcpcd/23125:
#0: ffff88807c0a6130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1780 [inline]
#0: ffff88807c0a6130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3264
2 locks held by dhcpcd-run-hook/23131:

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
<TASK>
dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
watchdog+0xf59/0xfa0 kernel/hung_task.c:379
kthread+0x2fa/0x390 kernel/kthread.c:388
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 23132 Comm: dhcpcd-run-hook Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__rcu_read_unlock+0xd/0xd0 kernel/rcu/tree_plugin.h:419
Code: 80 c1 03 38 c1 7c e3 48 89 df e8 9e dc 6d 00 eb d9 66 2e 0f 1f 84 00 00 00 00 00 66 90 f3 0f 1e fa 41 57 41 56 41 55 41 54 53 <49> bf 00 00 00 00 00 fc ff df 65 48 8b 3d 81 37 92 7e 48 8d 9f 3c
RSP: 0018:ffffc90003327170 EFLAGS: 00000093
RAX: ffffffff8190ce96 RBX: ffffffff8190ca63 RCX: ffff888023f68000
RDX: 0000000000000000 RSI: ffffffff8b1cfa00 RDI: ffffffff8b1cf9c0
RBP: ffffc90003327298 R08: ffffc9000332722f R09: 0000000000000000
R10: ffffc90003327220 R11: fffff52000664e46 R12: 0000000000000000
R13: 1ffff92000664e40 R14: ffff88806bd5c7a8 R15: 0000000000000000
FS: 00007fdb1ec9ec80(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdb1ef027e8 CR3: 000000007d259000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<TASK>
rcu_read_unlock include/linux/rcupdate.h:818 [inline]
trace_call_bpf+0x5ce/0x6c0 kernel/trace/bpf_trace.c:145
perf_trace_run_bpf_submit+0x7a/0x1c0 kernel/events/core.c:10287
perf_trace_preemptirq_template+0x269/0x330 include/trace/events/preemptirq.h:14
trace_irq_disable+0xbb/0xe0 include/trace/events/preemptirq.h:36
percpu_counter_add_batch+0xda/0x2a0 lib/percpu_counter.c:92
percpu_counter_add include/linux/percpu_counter.h:69 [inline]
add_mm_counter include/linux/mm.h:2629 [inline]
add_mm_rss_vec+0xe3/0x310 mm/memory.c:479
copy_pte_range mm/memory.c:1106 [inline]
copy_pmd_range mm/memory.c:1168 [inline]
copy_pud_range mm/memory.c:1205 [inline]
copy_p4d_range mm/memory.c:1229 [inline]
copy_page_range+0x2bd8/0x3700 mm/memory.c:1323
dup_mmap kernel/fork.c:769 [inline]
dup_mm kernel/fork.c:1694 [inline]
copy_mm+0x1751/0x1e30 kernel/fork.c:1743
copy_process+0x171d/0x3df0 kernel/fork.c:2508
kernel_clone+0x24b/0x8a0 kernel/fork.c:2917
__do_sys_clone kernel/fork.c:3060 [inline]
__se_sys_clone kernel/fork.c:3044 [inline]
__x64_sys_clone+0x1b7/0x230 kernel/fork.c:3044
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdb1ee38636
Code: 89 df e8 6d e8 f6 ff 45 31 c0 31 d2 31 f6 64 48 8b 04 25 10 00 00 00 bf 11 00 20 01 4c 8d 90 d0 02 00 00 b8 38 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 52 89 c5 85 c0 75 31 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffcd3234d80 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffcd3234d88 RCX: 00007fdb1ee38636
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 000055d7ad557e60 R08: 0000000000000000 R09: 0000000000000000
R10: 00007fdb1ec9ef50 R11: 0000000000000246 R12: 000055d7ad559f70
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>


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