syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.5.1960/13640 is trying to acquire lock:
ffff88807e083c68 (&pipe->mutex){+.+.}-{4:4}, at: anon_pipe_write+0x15d/0x1a90 fs/pipe.c:458

but task is already holding lock:
ffff8880335b2940 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
ffff8880335b2940 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x4a6/0xd60 fs/autofs/waitq.c:164

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sbi->pipe_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760
       autofs_write fs/autofs/waitq.c:55 [inline]
       autofs_notify_daemon+0x4a6/0xd60 fs/autofs/waitq.c:164
       autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426
       autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255
       autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401
       follow_automount fs/namei.c:1455 [inline]
       __traverse_mounts+0x192/0x790 fs/namei.c:1500
       traverse_mounts fs/namei.c:1529 [inline]
       handle_mounts fs/namei.c:1632 [inline]
       step_into+0x5aa/0x2270 fs/namei.c:1967
       walk_component+0xfc/0x5b0 fs/namei.c:2135
       lookup_last fs/namei.c:2630 [inline]
       path_lookupat+0x142/0x6d0 fs/namei.c:2654
       filename_lookup+0x224/0x5f0 fs/namei.c:2683
       kern_path+0x35/0x50 fs/namei.c:2816
       lookup_bdev+0xd8/0x280 block/bdev.c:1205
       resume_store+0x1d6/0x460 kernel/power/hibernate.c:1295
       kobj_attr_store+0x55/0x80 lib/kobject.c:840
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x7d0/0x11d0 fs/read_write.c:686
       ksys_write+0x12a/0x250 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&of->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760
       kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325
       iter_file_splice_write+0xa24/0x12e0 fs/splice.c:738
       do_splice_from fs/splice.c:938 [inline]
       do_splice+0x1478/0x1fc0 fs/splice.c:1351
       __do_splice+0x32a/0x360 fs/splice.c:1433
       __do_sys_splice fs/splice.c:1636 [inline]
       __se_sys_splice fs/splice.c:1618 [inline]
       __x64_sys_splice+0x187/0x250 fs/splice.c:1618
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&pipe->mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:598 [inline]
       __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760
       anon_pipe_write+0x15d/0x1a90 fs/pipe.c:458
       __kernel_write_iter+0x71d/0xb10 fs/read_write.c:619
       __kernel_write+0xf5/0x140 fs/read_write.c:639
       autofs_write fs/autofs/waitq.c:57 [inline]
       autofs_notify_daemon+0x4db/0xd60 fs/autofs/waitq.c:164
       autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426
       autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255
       autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401
       follow_automount fs/namei.c:1455 [inline]
       __traverse_mounts+0x192/0x790 fs/namei.c:1500
       traverse_mounts fs/namei.c:1529 [inline]
       handle_mounts fs/namei.c:1632 [inline]
       step_into+0x5aa/0x2270 fs/namei.c:1967
       walk_component+0xfc/0x5b0 fs/namei.c:2135
       lookup_last fs/namei.c:2630 [inline]
       path_lookupat+0x142/0x6d0 fs/namei.c:2654
       filename_lookup+0x224/0x5f0 fs/namei.c:2683
       kern_path+0x35/0x50 fs/namei.c:2816
       lookup_bdev+0xd8/0x280 block/bdev.c:1205
       resume_store+0x1d6/0x460 kernel/power/hibernate.c:1295
       kobj_attr_store+0x55/0x80 lib/kobject.c:840
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x7d0/0x11d0 fs/read_write.c:686
       ksys_write+0x12a/0x250 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &pipe->mutex --> &of->mutex --> &sbi->pipe_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sbi->pipe_mutex);
                               lock(&of->mutex);
                               lock(&sbi->pipe_mutex);
  lock(&pipe->mutex);

 *** DEADLOCK ***

5 locks held by syz.5.1960/13640:
 #0: ffff8880662bf0b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1232
 #1: ffff88807b740428 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738
 #2: ffff88802b976888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325
 #3: ffff88801eec21e8 (kn->active#64){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326
 #4: ffff8880335b2940 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
 #4: ffff8880335b2940 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x4a6/0xd60 fs/autofs/waitq.c:164

stack backtrace:
CPU: 0 UID: 0 PID: 13640 Comm: syz.5.1960 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043
 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:598 [inline]
 __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760
 anon_pipe_write+0x15d/0x1a90 fs/pipe.c:458
 __kernel_write_iter+0x71d/0xb10 fs/read_write.c:619
 __kernel_write+0xf5/0x140 fs/read_write.c:639
 autofs_write fs/autofs/waitq.c:57 [inline]
 autofs_notify_daemon+0x4db/0xd60 fs/autofs/waitq.c:164
 autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426
 autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255
 autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401
 follow_automount fs/namei.c:1455 [inline]
 __traverse_mounts+0x192/0x790 fs/namei.c:1500
 traverse_mounts fs/namei.c:1529 [inline]
 handle_mounts fs/namei.c:1632 [inline]
 step_into+0x5aa/0x2270 fs/namei.c:1967
 walk_component+0xfc/0x5b0 fs/namei.c:2135
 lookup_last fs/namei.c:2630 [inline]
 path_lookupat+0x142/0x6d0 fs/namei.c:2654
 filename_lookup+0x224/0x5f0 fs/namei.c:2683
 kern_path+0x35/0x50 fs/namei.c:2816
 lookup_bdev+0xd8/0x280 block/bdev.c:1205
 resume_store+0x1d6/0x460 kernel/power/hibernate.c:1295
 kobj_attr_store+0x55/0x80 lib/kobject.c:840
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x354/0x510 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x7d0/0x11d0 fs/read_write.c:686
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f125a78ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f125b564038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f125a9c5fa0 RCX: 00007f125a78ebe9
RDX: 0000000000000012 RSI: 0000200000000040 RDI: 0000000000000003
RBP: 00007f125a811e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f125a9c6038 R14: 00007f125a9c5fa0 R15: 00007ffeccf47ec8
 </TASK>
PM: Image not found (code -5)