syzbot

======================================================
WARNING: possible circular locking dependency detected
6.12.0-rc7-syzkaller-00212-g4a5df3796467 #0 Not tainted
------------------------------------------------------
syz.6.11503/15201 is trying to acquire lock:
ffff88805edd1088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325

but task is already holding lock:
ffff888047ffec68 (&pipe->mutex){+.+.}-{3:3}, at: iter_file_splice_write+0x330/0x1510 fs/splice.c:687

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&pipe->mutex){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       iter_file_splice_write+0x330/0x1510 fs/splice.c:687
       backing_file_splice_write+0x339/0x580 fs/backing-file.c:315
       ovl_splice_write+0x3c8/0x490 fs/overlayfs/file.c:383
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd68/0x18e0 fs/splice.c:1354
       __do_splice fs/splice.c:1436 [inline]
       __do_sys_splice fs/splice.c:1652 [inline]
       __se_sys_splice+0x331/0x4a0 fs/splice.c:1634
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (sb_writers#5){.+.+}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1716 [inline]
       sb_start_write+0x4d/0x1c0 include/linux/fs.h:1852
       mnt_want_write+0x3f/0x90 fs/namespace.c:515
       ovl_create_object+0x13a/0x3a0 fs/overlayfs/dir.c:642
       lookup_open fs/namei.c:3595 [inline]
       open_last_lookups fs/namei.c:3694 [inline]
       path_openat+0x1c03/0x3590 fs/namei.c:3930
       do_filp_open+0x235/0x490 fs/namei.c:3960
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1415
       do_sys_open fs/open.c:1430 [inline]
       __do_sys_openat fs/open.c:1446 [inline]
       __se_sys_openat fs/open.c:1441 [inline]
       __x64_sys_openat+0x247/0x2a0 fs/open.c:1441
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1524
       inode_lock_shared include/linux/fs.h:825 [inline]
       lookup_slow+0x45/0x70 fs/namei.c:1748
       walk_component+0x2e1/0x410 fs/namei.c:2053
       lookup_last fs/namei.c:2556 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2580
       filename_lookup+0x256/0x610 fs/namei.c:2609
       kern_path+0x35/0x50 fs/namei.c:2717
       lookup_bdev+0xc5/0x290 block/bdev.c:1164
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1239
       kernfs_fop_write_iter+0x3a0/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:590 [inline]
       vfs_write+0xaeb/0xd30 fs/read_write.c:683
       ksys_write+0x183/0x2b0 fs/read_write.c:736
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&of->mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3161 [inline]
       check_prevs_add kernel/locking/lockdep.c:3280 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3904
       __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325
       iter_file_splice_write+0xbfa/0x1510 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd68/0x18e0 fs/splice.c:1354
       __do_splice fs/splice.c:1436 [inline]
       __do_sys_splice fs/splice.c:1652 [inline]
       __se_sys_splice+0x331/0x4a0 fs/splice.c:1634
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &of->mutex --> sb_writers#5 --> &pipe->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pipe->mutex);
                               lock(sb_writers#5);
                               lock(&pipe->mutex);
  lock(&of->mutex);

 *** DEADLOCK ***

2 locks held by syz.6.11503/15201:
 #0: ffff88807d0bc420 (sb_writers#11){.+.+}-{0:0}, at: do_splice+0xce4/0x18e0 fs/splice.c:1353
 #1: ffff888047ffec68 (&pipe->mutex){+.+.}-{3:3}, at: iter_file_splice_write+0x330/0x1510 fs/splice.c:687

stack backtrace:
CPU: 1 UID: 0 PID: 15201 Comm: syz.6.11503 Not tainted 6.12.0-rc7-syzkaller-00212-g4a5df3796467 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
 check_noncircular+0x36a/0x4a0 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+0x18ef/0x5920 kernel/locking/lockdep.c:3904
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5202
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325
 iter_file_splice_write+0xbfa/0x1510 fs/splice.c:743
 do_splice_from fs/splice.c:941 [inline]
 do_splice+0xd68/0x18e0 fs/splice.c:1354
 __do_splice fs/splice.c:1436 [inline]
 __do_sys_splice fs/splice.c:1652 [inline]
 __se_sys_splice+0x331/0x4a0 fs/splice.c:1634
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f43ccf7e719
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:00007f43cde57038 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f43cd135f80 RCX: 00007f43ccf7e719
RDX: 0000000000000009 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 00007f43ccff175e R08: 0000000000000008 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f43cd135f80 R15: 00007ffc3a5236e8
 </TASK>