syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.3.2709/16941 is trying to acquire lock:
ffff88805ac22c68 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline]
ffff88805ac22c68 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x69/0x80 fs/pipe.c:88

but task is already holding lock:
ffff8880352a0420 (sb_writers#6){.+.+}-{0:0}, at: __do_splice+0x33b/0x370 fs/splice.c:1433

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (sb_writers#6){.+.+}-{0:0}:
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
       __sb_start_write include/linux/fs/super.h:19 [inline]
       sb_start_write include/linux/fs/super.h:125 [inline]
       mnt_want_write+0x6f/0x450 fs/namespace.c:493
       ovl_create_object+0x12b/0x3b0 fs/overlayfs/dir.c:691
       lookup_open.isra.0+0xc47/0x11b0 fs/namei.c:4483
       open_last_lookups fs/namei.c:4583 [inline]
       path_openat+0x2291/0x31a0 fs/namei.c:4827
       do_file_open+0x20e/0x430 fs/namei.c:4859
       do_sys_openat2+0x10d/0x1e0 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x12d/0x210 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}:
       down_read+0x99/0x460 kernel/locking/rwsem.c:1537
       inode_lock_shared include/linux/fs.h:1043 [inline]
       lookup_slow+0x42/0x70 fs/namei.c:1932
       walk_component fs/namei.c:2279 [inline]
       lookup_last fs/namei.c:2780 [inline]
       path_lookupat+0x5e8/0xc40 fs/namei.c:2804
       filename_lookup+0x202/0x590 fs/namei.c:2833
       kern_path+0x37/0x50 fs/namei.c:3040
       lookup_bdev+0xd8/0x280 block/bdev.c:1221
       resume_store+0x1d6/0x460 kernel/power/hibernate.c:1306
       kobj_attr_store+0x58/0x80 lib/kobject.c:840
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142
       kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:352
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x6ac/0x1070 fs/read_write.c:688
       ksys_write+0x12a/0x250 fs/read_write.c:740
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x106/0xf80 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:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       kernfs_fop_write_iter+0x2c2/0x5f0 fs/kernfs/file.c:343
       iter_file_splice_write+0x82b/0x10a0 fs/splice.c:738
       do_splice_from fs/splice.c:938 [inline]
       do_splice+0x109c/0x1fd0 fs/splice.c:1351
       __do_splice+0x33b/0x370 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+0x106/0xf80 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+0x14b8/0x2630 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       pipe_lock fs/pipe.c:91 [inline]
       pipe_lock+0x69/0x80 fs/pipe.c:88
       iter_file_splice_write+0x1f8/0x10a0 fs/splice.c:683
       do_splice_from fs/splice.c:938 [inline]
       do_splice+0x109c/0x1fd0 fs/splice.c:1351
       __do_splice+0x33b/0x370 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+0x106/0xf80 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:
  &pipe->mutex --> &ovl_i_mutex_dir_key[depth]#2 --> sb_writers#6

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_writers#6);
                               lock(&ovl_i_mutex_dir_key[depth]#2);
                               lock(sb_writers#6);
  lock(&pipe->mutex);

 *** DEADLOCK ***

1 lock held by syz.3.2709/16941:
 #0: ffff8880352a0420 (sb_writers#6){.+.+}-{0:0}, at: __do_splice+0x33b/0x370 fs/splice.c:1433

stack backtrace:
CPU: 1 UID: 0 PID: 16941 Comm: syz.3.2709 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 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+0x14b8/0x2630 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1cf/0x380 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:614 [inline]
 __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
 pipe_lock fs/pipe.c:91 [inline]
 pipe_lock+0x69/0x80 fs/pipe.c:88
 iter_file_splice_write+0x1f8/0x10a0 fs/splice.c:683
 do_splice_from fs/splice.c:938 [inline]
 do_splice+0x109c/0x1fd0 fs/splice.c:1351
 __do_splice+0x33b/0x370 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+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd79d79bf79
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:00007fd79e6a5028 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007fd79da15fa0 RCX: 00007fd79d79bf79
RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 00007fd79d8327e0 R08: 0000000000001000 R09: 0800000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd79da16038 R14: 00007fd79da15fa0 R15: 00007fff47ac62d8
 </TASK>