syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 Not tainted
------------------------------------------------------
syz.0.3700/21889 is trying to acquire lock:
ffff88804f649c88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325

but task is already holding lock:
ffff88807e31d468 (&pipe->mutex){+.+.}-{4:4}, at: iter_file_splice_write+0x1e6/0x1000 fs/splice.c:683

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&pipe->mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
       anon_pipe_write+0x16a/0x1360 fs/pipe.c:459
       __kernel_write_iter+0x3ec/0x860 fs/read_write.c:617
       __kernel_write+0xef/0x150 fs/read_write.c:637
       autofs_write fs/autofs/waitq.c:57 [inline]
       autofs_notify_daemon+0x748/0xe50 fs/autofs/waitq.c:164
       autofs_wait+0x11dc/0x1870 fs/autofs/waitq.c:426
       autofs_do_expire_multi+0x5ca/0x9a0 fs/autofs/expire.c:593
       autofs_root_ioctl+0x46/0x60 fs/autofs/root.c:910
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:892
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&sbi->pipe_mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
       autofs_write fs/autofs/waitq.c:55 [inline]
       autofs_notify_daemon+0x735/0xe50 fs/autofs/waitq.c:164
       autofs_wait+0x11dc/0x1870 fs/autofs/waitq.c:426
       autofs_mount_wait+0x16b/0x330 fs/autofs/root.c:255
       autofs_d_automount+0x393/0x720 fs/autofs/root.c:401
       follow_automount fs/namei.c:1455 [inline]
       __traverse_mounts+0x308/0x5b0 fs/namei.c:1500
       traverse_mounts fs/namei.c:1529 [inline]
       handle_mounts fs/namei.c:1632 [inline]
       step_into+0x534/0xf30 fs/namei.c:1976
       lookup_last fs/namei.c:2636 [inline]
       path_lookupat+0x163/0x430 fs/namei.c:2660
       filename_lookup+0x212/0x570 fs/namei.c:2689
       kern_path+0x35/0x50 fs/namei.c:2822
       lookup_bdev+0xc0/0x280 block/bdev.c:1205
       resume_store+0x169/0x460 kernel/power/hibernate.c:1248
       kernfs_fop_write_iter+0x378/0x4f0 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:591 [inline]
       vfs_write+0x54b/0xa90 fs/read_write.c:684
       ksys_write+0x145/0x250 fs/read_write.c:736
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&of->mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
       __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
       kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325
       iter_file_splice_write+0x93a/0x1000 fs/splice.c:738
       do_splice_from fs/splice.c:935 [inline]
       do_splice+0xc79/0x1660 fs/splice.c:1348
       __do_splice fs/splice.c:1430 [inline]
       __do_sys_splice fs/splice.c:1633 [inline]
       __se_sys_splice+0x2e1/0x460 fs/splice.c:1615
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 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:
  &of->mutex --> &sbi->pipe_mutex --> &pipe->mutex

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

2 locks held by syz.0.3700/21889:
 #0: ffff8880346f0420 (sb_writers#7){.+.+}-{0:0}, at: do_splice+0xbff/0x1660 fs/splice.c:1347
 #1: ffff88807e31d468 (&pipe->mutex){+.+.}-{4:4}, at: iter_file_splice_write+0x1e6/0x1000 fs/splice.c:683

stack backtrace:
CPU: 0 UID: 0 PID: 21889 Comm: syz.0.3700 Not tainted 6.15.0-rc5-syzkaller-00275-gbec6f00f120e #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
 kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325
 iter_file_splice_write+0x93a/0x1000 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 do_splice+0xc79/0x1660 fs/splice.c:1348
 __do_splice fs/splice.c:1430 [inline]
 __do_sys_splice fs/splice.c:1633 [inline]
 __se_sys_splice+0x2e1/0x460 fs/splice.c:1615
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f087518e969
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:00007f087605c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f08753b6080 RCX: 00007f087518e969
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f0875210ab1 R08: 000000000000bfd1 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f08753b6080 R15: 00007fffe7ecd768
 </TASK>
kernel profiling enabled (shift: 9)