syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.8.2494/15030 is trying to acquire lock:
ffff888029aabc78 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343

but task is already holding lock:
ffff88802a292858 (&pipe->mutex){+.+.}-{4:4}, at: iter_file_splice_write+0x1e6/0x10b0 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}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       anon_pipe_write+0x160/0x1460 fs/pipe.c:458
       __kernel_write_iter+0x48a/0x920 fs/read_write.c:619
       __kernel_write+0xef/0x150 fs/read_write.c:639
       autofs_write fs/autofs/waitq.c:57 [inline]
       autofs_notify_daemon+0x721/0xe20 fs/autofs/waitq.c:164
       autofs_wait+0x11f7/0x1900 fs/autofs/waitq.c:426
       autofs_mount_wait+0x16b/0x390 fs/autofs/root.c:255
       autofs_d_automount+0x64f/0x820 fs/autofs/root.c:409
       follow_automount fs/namei.c:1499 [inline]
       __traverse_mounts+0x301/0x5e0 fs/namei.c:1552
       traverse_mounts fs/namei.c:1581 [inline]
       handle_mounts fs/namei.c:1686 [inline]
       step_into_slowpath+0x469/0x7d0 fs/namei.c:2043
       step_into fs/namei.c:2091 [inline]
       walk_component fs/namei.c:2227 [inline]
       lookup_last fs/namei.c:2722 [inline]
       path_lookupat+0x433/0x8c0 fs/namei.c:2746
       filename_lookup+0x212/0x570 fs/namei.c:2775
       kern_path+0x35/0x50 fs/namei.c:2987
       lookup_bdev+0xc0/0x280 block/bdev.c:1222
       resume_store+0x169/0x480 kernel/power/hibernate.c:1306
       kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x5d5/0xb40 fs/read_write.c:686
       ksys_write+0x14b/0x260 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&sbi->pipe_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       autofs_write fs/autofs/waitq.c:55 [inline]
       autofs_notify_daemon+0x70e/0xe20 fs/autofs/waitq.c:164
       autofs_wait+0x11f7/0x1900 fs/autofs/waitq.c:426
       autofs_mount_wait+0x16b/0x390 fs/autofs/root.c:255
       autofs_d_automount+0x64f/0x820 fs/autofs/root.c:409
       follow_automount fs/namei.c:1499 [inline]
       __traverse_mounts+0x301/0x5e0 fs/namei.c:1552
       traverse_mounts fs/namei.c:1581 [inline]
       handle_mounts fs/namei.c:1686 [inline]
       step_into_slowpath+0x469/0x7d0 fs/namei.c:2043
       step_into fs/namei.c:2091 [inline]
       walk_component fs/namei.c:2227 [inline]
       lookup_last fs/namei.c:2722 [inline]
       path_lookupat+0x433/0x8c0 fs/namei.c:2746
       filename_lookup+0x212/0x570 fs/namei.c:2775
       kern_path+0x35/0x50 fs/namei.c:2987
       lookup_bdev+0xc0/0x280 block/bdev.c:1222
       resume_store+0x169/0x480 kernel/power/hibernate.c:1306
       kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x5d5/0xb40 fs/read_write.c:686
       ksys_write+0x14b/0x260 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 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:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343
       iter_file_splice_write+0x977/0x10b0 fs/splice.c:738
       do_splice_from fs/splice.c:938 [inline]
       do_splice+0xc8e/0x1680 fs/splice.c:1351
       __do_splice fs/splice.c:1433 [inline]
       __do_sys_splice fs/splice.c:1636 [inline]
       __se_sys_splice+0x2e1/0x460 fs/splice.c:1618
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xec/0xf80 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.8.2494/15030:
 #0: ffff888033888480 (sb_writers#10){.+.+}-{0:0}, at: do_splice+0xc11/0x1680 fs/splice.c:1350
 #1: ffff88802a292858 (&pipe->mutex){+.+.}-{4:4}, at: iter_file_splice_write+0x1e6/0x10b0 fs/splice.c:683

stack backtrace:
CPU: 0 UID: 0 PID: 15030 Comm: syz.8.2494 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x107/0x340 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
 kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343
 iter_file_splice_write+0x977/0x10b0 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 do_splice+0xc8e/0x1680 fs/splice.c:1351
 __do_splice fs/splice.c:1433 [inline]
 __do_sys_splice fs/splice.c:1636 [inline]
 __se_sys_splice+0x2e1/0x460 fs/splice.c:1618
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f095a0df749
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:00007f0958346038 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f095a335fa0 RCX: 00007f095a0df749
RDX: 0000000000000006 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f095a163f91 R08: 0000000000001000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f095a336038 R14: 00007f095a335fa0 R15: 00007ffcd8ecd908
 </TASK>