syzbot

======================================================
WARNING: possible circular locking dependency detected
6.12.0-syzkaller-10689-g7af08b57bcb9 #0 Not tainted
------------------------------------------------------
syz.4.798/8993 is trying to acquire lock:
ffff888027f33468 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:92 [inline]
ffff888027f33468 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x64/0x80 fs/pipe.c:89

but task is already holding lock:
ffff888029b6a420 (sb_writers#6){.+.+}-{0:0}, at: __do_splice+0x327/0x360 fs/splice.c:1436

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 include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1725 [inline]
       sb_start_write include/linux/fs.h:1861 [inline]
       mnt_want_write+0x6f/0x450 fs/namespace.c:515
       ovl_create_object+0x12e/0x300 fs/overlayfs/dir.c:656
       lookup_open.isra.0+0x1174/0x14c0 fs/namei.c:3649
       open_last_lookups fs/namei.c:3748 [inline]
       path_openat+0x904/0x2d60 fs/namei.c:3984
       do_filp_open+0x20c/0x470 fs/namei.c:4014
       do_sys_openat2+0x17a/0x1e0 fs/open.c:1402
       do_sys_open fs/open.c:1417 [inline]
       __do_sys_openat fs/open.c:1433 [inline]
       __se_sys_openat fs/open.c:1428 [inline]
       __x64_sys_openat+0x175/0x210 fs/open.c:1428
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}:
       down_read+0x9a/0x330 kernel/locking/rwsem.c:1524
       inode_lock_shared include/linux/fs.h:828 [inline]
       lookup_slow fs/namei.c:1807 [inline]
       walk_component+0x342/0x5b0 fs/namei.c:2112
       lookup_last fs/namei.c:2610 [inline]
       path_lookupat+0x17f/0x770 fs/namei.c:2634
       filename_lookup+0x221/0x5f0 fs/namei.c:2663
       kern_path+0x35/0x50 fs/namei.c:2771
       lookup_bdev+0xd9/0x280 block/bdev.c:1164
       resume_store+0x1d8/0x460 kernel/power/hibernate.c:1242
       kobj_attr_store+0x55/0x80 lib/kobject.c:840
       sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:136
       kernfs_fop_write_iter+0x33d/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:586 [inline]
       vfs_write+0x5ae/0x1150 fs/read_write.c:679
       ksys_write+0x12b/0x250 fs/read_write.c:731
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&of->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19b/0xa60 kernel/locking/mutex.c:735
       kernfs_fop_write_iter+0x27b/0x500 fs/kernfs/file.c:325
       iter_file_splice_write+0x90f/0x10b0 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0x145c/0x1f60 fs/splice.c:1354
       __do_splice+0x327/0x360 fs/splice.c:1436
       __do_sys_splice fs/splice.c:1639 [inline]
       __se_sys_splice fs/splice.c:1621 [inline]
       __x64_sys_splice+0x187/0x250 fs/splice.c:1621
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&pipe->mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain kernel/locking/lockdep.c:3904 [inline]
       __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
       lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19b/0xa60 kernel/locking/mutex.c:735
       pipe_lock fs/pipe.c:92 [inline]
       pipe_lock+0x64/0x80 fs/pipe.c:89
       iter_file_splice_write+0x1eb/0x10b0 fs/splice.c:687
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0x145c/0x1f60 fs/splice.c:1354
       __do_splice+0x327/0x360 fs/splice.c:1436
       __do_sys_splice fs/splice.c:1639 [inline]
       __se_sys_splice fs/splice.c:1621 [inline]
       __x64_sys_splice+0x187/0x250 fs/splice.c:1621
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
       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.4.798/8993:
 #0: ffff888029b6a420 (sb_writers#6){.+.+}-{0:0}, at: __do_splice+0x327/0x360 fs/splice.c:1436

stack backtrace:
CPU: 1 UID: 0 PID: 8993 Comm: syz.4.798 Not tainted 6.12.0-syzkaller-10689-g7af08b57bcb9 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x419/0x5d0 kernel/locking/lockdep.c:2074
 check_noncircular+0x31a/0x400 kernel/locking/lockdep.c:2206
 check_prev_add kernel/locking/lockdep.c:3161 [inline]
 check_prevs_add kernel/locking/lockdep.c:3280 [inline]
 validate_chain kernel/locking/lockdep.c:3904 [inline]
 __lock_acquire+0x249e/0x3c40 kernel/locking/lockdep.c:5226
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x19b/0xa60 kernel/locking/mutex.c:735
 pipe_lock fs/pipe.c:92 [inline]
 pipe_lock+0x64/0x80 fs/pipe.c:89
 iter_file_splice_write+0x1eb/0x10b0 fs/splice.c:687
 do_splice_from fs/splice.c:941 [inline]
 do_splice+0x145c/0x1f60 fs/splice.c:1354
 __do_splice+0x327/0x360 fs/splice.c:1436
 __do_sys_splice fs/splice.c:1639 [inline]
 __se_sys_splice fs/splice.c:1621 [inline]
 __x64_sys_splice+0x187/0x250 fs/splice.c:1621
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5d3e380849
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:00007f5d3f221058 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f5d3e545fa0 RCX: 00007f5d3e380849
RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000000007
RBP: 00007f5d3e3f3986 R08: 0000000000000114 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f5d3e545fa0 R15: 00007ffd074cc9c8
 </TASK>