======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     Y
------------------------------------------------------
syz.4.3071/18744 is trying to acquire lock:
ffff88804c865938 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:68 [inline]
ffff88804c865938 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x75d/0xf10 fs/autofs/waitq.c:177

but task is already holding lock:
ffff888026fc2480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540 fs/kernfs/file.c:336

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&of->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821
       kernfs_fop_write_iter+0x1d8/0x540 fs/kernfs/file.c:336
       iter_file_splice_write+0xa31/0x1240 fs/splice.c:736
       do_splice_from fs/splice.c:936 [inline]
       do_splice+0xf9e/0x19f0 fs/splice.c:1377
       __do_splice fs/splice.c:1459 [inline]
       __do_sys_splice fs/splice.c:1662 [inline]
       __se_sys_splice+0x353/0x490 fs/splice.c:1644
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&pipe->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821
       anon_pipe_prefill_and_lock fs/pipe.c:165 [inline]
       anon_pipe_write+0x28f/0x1a90 fs/pipe.c:534
       __kernel_write_iter+0x44a/0x8f0 fs/read_write.c:621
       __kernel_write+0x106/0x170 fs/read_write.c:641
       autofs_write fs/autofs/waitq.c:70 [inline]
       autofs_notify_daemon+0x770/0xf10 fs/autofs/waitq.c:177
       autofs_wait+0x11aa/0x18a0 fs/autofs/waitq.c:439
       autofs_do_expire_multi+0x1dc/0x5c0 fs/autofs/expire.c:593
       autofs_root_ioctl+0x46/0x60 fs/autofs/root.c:913
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:597 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sbi->pipe_mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3209 [inline]
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821
       autofs_write fs/autofs/waitq.c:68 [inline]
       autofs_notify_daemon+0x75d/0xf10 fs/autofs/waitq.c:177
       autofs_wait+0x11aa/0x18a0 fs/autofs/waitq.c:439
       autofs_mount_wait+0x16b/0x390 fs/autofs/root.c:256
       autofs_d_automount+0x64e/0x810 fs/autofs/root.c:410
       follow_automount fs/namei.c:1565 [inline]
       __traverse_mounts+0x2fe/0x5d0 fs/namei.c:1618
       traverse_mounts fs/namei.c:1647 [inline]
       handle_mounts fs/namei.c:1749 [inline]
       step_into_slowpath+0x4ba/0x820 fs/namei.c:2104
       step_into fs/namei.c:2152 [inline]
       walk_component fs/namei.c:2288 [inline]
       lookup_last fs/namei.c:2789 [inline]
       path_lookupat+0x433/0x8c0 fs/namei.c:2813
       filename_lookup+0x265/0x5d0 fs/namei.c:2842
       kern_path+0x3d/0x150 fs/namei.c:3036
       lookup_bdev+0xc8/0x2b0 block/bdev.c:1268
       resume_store+0x181/0x500 kernel/power/hibernate.c:1286
       kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x612/0xba0 fs/read_write.c:687
       ksys_write+0x150/0x270 fs/read_write.c:739
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

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

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

locks held by syz.4.3071/18744: 4, last CPU#0:
 #0: ffff88807942a470 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x118/0x160 fs/file.c:1408
 #1: ffff88802620a460 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2758 [inline]
 #1: ffff88802620a460 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 fs/read_write.c:683
 #2: ffff888026fc2480 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540 fs/kernfs/file.c:336
 #3: ffff88801eed8698 (kn->active#59){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:73 [inline]
 #3: ffff88801eed8698 (kn->active#59){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x22b/0x540 fs/kernfs/file.c:337

stack backtrace:
CPU: 0 UID: 0 PID: 18744 Comm: syz.4.3071 Tainted: G             L     Y syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP, [Y]=FORCED_BIND
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
 check_prev_add kernel/locking/lockdep.c:3209 [inline]
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x197/0x15a0 kernel/locking/mutex.c:821
 autofs_write fs/autofs/waitq.c:68 [inline]
 autofs_notify_daemon+0x75d/0xf10 fs/autofs/waitq.c:177
 autofs_wait+0x11aa/0x18a0 fs/autofs/waitq.c:439
 autofs_mount_wait+0x16b/0x390 fs/autofs/root.c:256
 autofs_d_automount+0x64e/0x810 fs/autofs/root.c:410
 follow_automount fs/namei.c:1565 [inline]
 __traverse_mounts+0x2fe/0x5d0 fs/namei.c:1618
 traverse_mounts fs/namei.c:1647 [inline]
 handle_mounts fs/namei.c:1749 [inline]
 step_into_slowpath+0x4ba/0x820 fs/namei.c:2104
 step_into fs/namei.c:2152 [inline]
 walk_component fs/namei.c:2288 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x433/0x8c0 fs/namei.c:2813
 filename_lookup+0x265/0x5d0 fs/namei.c:2842
 kern_path+0x3d/0x150 fs/namei.c:3036
 lookup_bdev+0xc8/0x2b0 block/bdev.c:1268
 resume_store+0x181/0x500 kernel/power/hibernate.c:1286
 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f216879f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2169677028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2168a26180 RCX: 00007f216879f559
RDX: 0000000000000012 RSI: 00002000000003c0 RDI: 000000000000000a
RBP: 00007f2168836b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2168a26218 R14: 00007f2168a26180 R15: 00007ffe851a2248
 </TASK>