syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc5-syzkaller-00158-g3013c33dcbd9 #0 Not tainted
------------------------------------------------------
syz.7.4441/24880 is trying to acquire lock:
ffff8880606a1140 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_write fs/autofs/waitq.c:55 [inline]
ffff8880606a1140 (&sbi->pipe_mutex){+.+.}-{4:4}, at: autofs_notify_daemon+0x735/0xe50 fs/autofs/waitq.c:164

but task is already holding lock:
ffff888065042088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&of->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
       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

-> #1 (&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_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
       open_last_lookups fs/namei.c:3827 [inline]
       path_openat+0x1bc6/0x3830 fs/namei.c:4036
       do_filp_open+0x1fa/0x410 fs/namei.c:4066
       do_sys_openat2+0x121/0x1c0 fs/open.c:1429
       do_sys_open fs/open.c:1444 [inline]
       __do_sys_openat fs/open.c:1460 [inline]
       __se_sys_openat fs/open.c:1455 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1455
       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 (&sbi->pipe_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
       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

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 ***

4 locks held by syz.7.4441/24880:
 #0: ffff88807ba32ef8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1213
 #1: ffff888030082420 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3041 [inline]
 #1: ffff888030082420 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x211/0xa90 fs/read_write.c:680
 #2: ffff888065042088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325
 #3: ffff8881416e3878 (kn->active#66){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x203/0x4f0 fs/kernfs/file.c:326

stack backtrace:
CPU: 1 UID: 0 PID: 24880 Comm: syz.7.4441 Not tainted 6.15.0-rc5-syzkaller-00158-g3013c33dcbd9 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
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
 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
RIP: 0033:0x7feb9b98e969
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:00007feb997f6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007feb9bbb5fa0 RCX: 00007feb9b98e969
RDX: 0000000000000012 RSI: 0000200000000000 RDI: 0000000000000007
RBP: 00007feb9ba10ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007feb9bbb5fa0 R15: 00007ffc4a4a9b78
 </TASK>
PM: Image not found (code -6)