syzbot

======================================================
WARNING: possible circular locking dependency detected
6.14.0-rc4-syzkaller #0 Not tainted
------------------------------------------------------
syz.7.1491/13055 is trying to acquire lock:
ffff88807baac868 (&pipe->mutex){+.+.}-{4:4}, at: iter_file_splice_write+0x330/0x1510 fs/splice.c:687

but task is already holding lock:
ffff88806664e420 (sb_writers#5){.+.+}-{0:0}, at: do_splice+0xce4/0x18b0 fs/splice.c:1353

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (sb_writers#5){.+.+}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1785 [inline]
       sb_start_write include/linux/fs.h:1921 [inline]
       ovl_start_write+0x11d/0x290 fs/overlayfs/util.c:31
       ovl_do_copy_up fs/overlayfs/copy_up.c:990 [inline]
       ovl_copy_up_one fs/overlayfs/copy_up.c:1202 [inline]
       ovl_copy_up_flags+0x1145/0x47c0 fs/overlayfs/copy_up.c:1257
       ovl_nlink_start+0x9c/0x400 fs/overlayfs/util.c:1165
       ovl_do_remove+0x1fa/0xd90 fs/overlayfs/dir.c:920
       vfs_rmdir+0x3a5/0x510 fs/namei.c:4396
       do_rmdir+0x3b5/0x580 fs/namei.c:4455
       __do_sys_rmdir fs/namei.c:4474 [inline]
       __se_sys_rmdir fs/namei.c:4472 [inline]
       __x64_sys_rmdir+0x47/0x50 fs/namei.c:4472
       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

-> #3 (&ovl_i_lock_key[depth]){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:650 [inline]
       ovl_copy_up_start+0x53/0x310 fs/overlayfs/util.c:727
       ovl_copy_up_one fs/overlayfs/copy_up.c:1195 [inline]
       ovl_copy_up_flags+0xcfe/0x47c0 fs/overlayfs/copy_up.c:1257
       ovl_nlink_start+0x9c/0x400 fs/overlayfs/util.c:1165
       ovl_do_remove+0x1fa/0xd90 fs/overlayfs/dir.c:920
       vfs_rmdir+0x3a5/0x510 fs/namei.c:4396
       do_rmdir+0x3b5/0x580 fs/namei.c:4455
       __do_sys_rmdir fs/namei.c:4474 [inline]
       __se_sys_rmdir fs/namei.c:4472 [inline]
       __x64_sys_rmdir+0x47/0x50 fs/namei.c:4472
       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 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1524
       inode_lock_shared include/linux/fs.h:887 [inline]
       lookup_slow+0x45/0x70 fs/namei.c:1809
       walk_component+0x2e1/0x410 fs/namei.c:2114
       lookup_last fs/namei.c:2612 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2636
       filename_lookup+0x2a3/0x670 fs/namei.c:2665
       kern_path+0x35/0x50 fs/namei.c:2773
       lookup_bdev+0xc5/0x290 block/bdev.c:1163
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1247
       kernfs_fop_write_iter+0x3a2/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:586 [inline]
       vfs_write+0xad1/0xd10 fs/read_write.c:679
       ksys_write+0x18f/0x2b0 fs/read_write.c:731
       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 (&of->mutex){+.+.}-{4:4}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325
       iter_file_splice_write+0xbfc/0x1510 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd6a/0x18b0 fs/splice.c:1354
       __do_splice fs/splice.c:1436 [inline]
       __do_sys_splice fs/splice.c:1639 [inline]
       __se_sys_splice+0x2e0/0x450 fs/splice.c:1621
       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 (&pipe->mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3163 [inline]
       check_prevs_add kernel/locking/lockdep.c:3282 [inline]
       validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
       __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
       __mutex_lock_common kernel/locking/mutex.c:585 [inline]
       __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
       iter_file_splice_write+0x330/0x1510 fs/splice.c:687
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd6a/0x18b0 fs/splice.c:1354
       __do_splice fs/splice.c:1436 [inline]
       __do_sys_splice fs/splice.c:1639 [inline]
       __se_sys_splice+0x2e0/0x450 fs/splice.c:1621
       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:
  &pipe->mutex --> &ovl_i_lock_key[depth] --> sb_writers#5

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_writers#5);
                               lock(&ovl_i_lock_key[depth]);
                               lock(sb_writers#5);
  lock(&pipe->mutex);

 *** DEADLOCK ***

1 lock held by syz.7.1491/13055:
 #0: ffff88806664e420 (sb_writers#5){.+.+}-{0:0}, at: do_splice+0xce4/0x18b0 fs/splice.c:1353

stack backtrace:
CPU: 1 UID: 0 PID: 13055 Comm: syz.7.1491 Not tainted 6.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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:2076
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2208
 check_prev_add kernel/locking/lockdep.c:3163 [inline]
 check_prevs_add kernel/locking/lockdep.c:3282 [inline]
 validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3906
 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851
 __mutex_lock_common kernel/locking/mutex.c:585 [inline]
 __mutex_lock+0x19c/0x1010 kernel/locking/mutex.c:730
 iter_file_splice_write+0x330/0x1510 fs/splice.c:687
 do_splice_from fs/splice.c:941 [inline]
 do_splice+0xd6a/0x18b0 fs/splice.c:1354
 __do_splice fs/splice.c:1436 [inline]
 __do_sys_splice fs/splice.c:1639 [inline]
 __se_sys_splice+0x2e0/0x450 fs/splice.c:1621
 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: 0033:0x7f0290f8d169
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:00007f0291d5b038 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f02911a6160 RCX: 00007f0290f8d169
RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f029100e2a0 R08: 0000000000000006 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f02911a6160 R15: 00007ffe5f45ef98
 </TASK>