[v6.1] INFO: task hung in __fdget_pos

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syzbot

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Oct 8, 2023, 9:13:50 AM10/8/23
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Hello,

syzbot found the following issue on:

HEAD commit: ecda77b46871 Linux 6.1.56
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10b7f02e680000
kernel config: https://syzkaller.appspot.com/x/.config?x=e82fa6f6f9ab7d72
dashboard link: https://syzkaller.appspot.com/bug?extid=db2e096c5b69cc5a0e57
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0b7814b5111f/disk-ecda77b4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f23a3c686699/vmlinux-ecda77b4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/474cde37da7a/bzImage-ecda77b4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+db2e09...@syzkaller.appspotmail.com

INFO: task syz-executor.2:18783 blocked for more than 143 seconds.
Not tainted 6.1.56-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.2 state:D stack:29096 pid:18783 ppid:3598 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5241 [inline]
__schedule+0x142d/0x4550 kernel/sched/core.c:6554
schedule+0xbf/0x180 kernel/sched/core.c:6630
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6689
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0x6b9/0xd80 kernel/locking/mutex.c:747
__fdget_pos+0x2ba/0x360 fs/file.c:1062
fdget_pos include/linux/file.h:73 [inline]
__do_sys_getdents fs/readdir.c:282 [inline]
__se_sys_getdents+0x1bf/0x4c0 fs/readdir.c:271
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f56faa7cae9
RSP: 002b:00007f56fb7000c8 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f56fab9c050 RCX: 00007f56faa7cae9
RDX: 0000000000000056 RSI: 0000000020000580 RDI: 0000000000000005
RBP: 00007f56faac847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f56fab9c050 R15: 00007fff7fdca058
</TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8d12a170 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xe30 kernel/rcu/tasks.h:516
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8d12a970 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x29/0xe30 kernel/rcu/tasks.h:516
1 lock held by khungtaskd/28:
#0: ffffffff8d129fa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:306 [inline]
#0: ffffffff8d129fa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
#0: ffffffff8d129fa0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6493
1 lock held by udevd/3005:
2 locks held by getty/3315:
#0: ffff888028abb098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc900031262f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6a7/0x1db0 drivers/tty/n_tty.c:2188
3 locks held by syz-executor.4/3594:
2 locks held by kworker/u4:6/3692:
2 locks held by kworker/u4:18/11423:
#0: ffff888012479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
#1: ffffc9000b64fd20 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
2 locks held by kworker/0:12/11564:
#0: ffff888012472538 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
#1: ffffc900150cfd20 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7a9/0x11d0 kernel/workqueue.c:2267
3 locks held by syz-executor.2/18773:
1 lock held by syz-executor.2/18783:
#0: ffff8880977bf4e8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2ba/0x360 fs/file.c:1062
2 locks held by syz-executor.1/21226:
#0: ffff888070b21410 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
#0: ffff888070b21410 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: __sock_release net/socket.c:651 [inline]
#0: ffff888070b21410 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: sock_close+0x98/0x230 net/socket.c:1370
#1: ffffffff8d12f578 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
#1: ffffffff8d12f578 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x3b0/0x8a0 kernel/rcu/tree_exp.h:950
1 lock held by syz-executor.1/21229:
#0: ffffffff8e29b828 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffffffff8e29b828 (rtnl_mutex){+.+.}-{3:3}, at: __rtnl_newlink net/core/rtnetlink.c:3600 [inline]
#0: ffffffff8e29b828 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_newlink+0xadf/0x2050 net/core/rtnetlink.c:3623
2 locks held by syz-executor.0/21228:
#0: ffff888070b22010 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:756 [inline]
#0: ffff888070b22010 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: __sock_release net/socket.c:651 [inline]
#0: ffff888070b22010 (&sb->s_type->i_mutex_key#10){+.+.}-{3:3}, at: sock_close+0x98/0x230 net/socket.c:1370
#1: ffffffff8d12f578 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:324 [inline]
#1: ffffffff8d12f578 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x479/0x8a0 kernel/rcu/tree_exp.h:950
1 lock held by syz-executor.4/21247:
#0: ffffffff8e29b828 (rtnl_mutex){+.+.}-{3:3}, at: tun_detach drivers/net/tun.c:697 [inline]
#0: ffffffff8e29b828 (rtnl_mutex){+.+.}-{3:3}, at: tun_chr_close+0x3a/0x1b0 drivers/net/tun.c:3477

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted 6.1.56-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
nmi_cpu_backtrace+0x4e1/0x560 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1b0/0x3f0 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+0xf88/0xfd0 kernel/hung_task.c:377
kthread+0x28d/0x320 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3607 Comm: syz-executor.5 Not tainted 6.1.56-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
RIP: 0010:copy_present_pte mm/memory.c:948 [inline]
RIP: 0010:copy_pte_range mm/memory.c:1081 [inline]
RIP: 0010:copy_pmd_range mm/memory.c:1167 [inline]
RIP: 0010:copy_pud_range mm/memory.c:1204 [inline]
RIP: 0010:copy_p4d_range mm/memory.c:1228 [inline]
RIP: 0010:copy_page_range+0x187b/0x4660 mm/memory.c:1326
Code: 1f e8 89 c1 be ff 4c 89 ff be 08 00 00 00 e8 dc ea 15 00 f0 41 80 27 fd 48 83 64 24 28 fd eb 05 e8 6a c1 be ff 48 8b 44 24 18 <48> 85 c0 0f 84 91 00 00 00 4c 8d 70 08 4d 89 f7 49 c1 ef 03 48 b8
RSP: 0018:ffffc9000410f4c0 EFLAGS: 00000293
RAX: ffffea000207b640 RBX: 0000000000000002 RCX: ffff888074a8bb80
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000000
RBP: ffffc9000410f870 R08: ffffffff81cbaf57 R09: fffff9400040f6c9
R10: 0000000000000000 R11: dffffc0000000001 R12: ffff88802999aa20
R13: 0000000000000000 R14: 0000000000000028 R15: ffff8880887158d0
FS: 00005555564cb480(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f36e9f7a1f8 CR3: 000000008870d000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<NMI>
</NMI>
<TASK>
dup_mmap kernel/fork.c:696 [inline]
dup_mm kernel/fork.c:1540 [inline]
copy_mm+0xf42/0x1990 kernel/fork.c:1589
copy_process+0x19d5/0x4060 kernel/fork.c:2267
kernel_clone+0x222/0x920 kernel/fork.c:2682
__do_sys_clone kernel/fork.c:2823 [inline]
__se_sys_clone kernel/fork.c:2807 [inline]
__x64_sys_clone+0x231/0x280 kernel/fork.c:2807
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f453f679b13
Code: 1f 84 00 00 00 00 00 64 48 8b 04 25 10 00 00 00 45 31 c0 31 d2 31 f6 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 35 89 c2 85 c0 75 2c 64 48 8b 04 25 10 00 00
RSP: 002b:00007ffc43e39b38 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f453f679b13
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 00005555564cb750 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001
</TASK>


---
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syzbot

unread,
Jan 16, 2024, 8:13:11 AMJan 16
to syzkaller...@googlegroups.com
Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.
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