syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc3-syzkaller-00342-g5bc1018675ec #0 Not tainted
------------------------------------------------------
syz.9.1492/22135 is trying to acquire lock:
ffff88803400e868 (&pipe->mutex){+.+.}-{4:4}, at: iter_file_splice_write+0x1e6/0x1000 fs/splice.c:683

but task is already holding lock:
ffff88805bc52420 (sb_writers#5){.+.+}-{0:0}, at: do_splice+0xbff/0x1660 fs/splice.c:1347

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (sb_writers#5){.+.+}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
       __sb_start_write include/linux/fs.h:1783 [inline]
       sb_start_write+0x4d/0x1c0 include/linux/fs.h:1919
       mnt_want_write+0x41/0x90 fs/namespace.c:556
       ovl_setattr+0x2c8/0x550 fs/overlayfs/inode.c:76
       notify_change+0xb33/0xe40 fs/attr.c:552
       chown_common+0x3f9/0x5a0 fs/open.c:782
       do_fchownat+0x161/0x270 fs/open.c:813
       __do_sys_chown fs/open.c:833 [inline]
       __se_sys_chown fs/open.c:831 [inline]
       __x64_sys_chown+0x82/0xa0 fs/open.c:831
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1524
       inode_lock_shared include/linux/fs.h:877 [inline]
       lookup_slow+0x46/0x70 fs/namei.c:1833
       walk_component+0x2d2/0x400 fs/namei.c:2138
       lookup_last fs/namei.c:2636 [inline]
       path_lookupat+0x163/0x430 fs/namei.c:2660
       filename_lookup+0x212/0x570 fs/namei.c:2689
       kern_path+0x35/0x50 fs/namei.c:2822
       lookup_bdev+0xc0/0x280 block/bdev.c:1205
       resume_store+0x169/0x460 kernel/power/hibernate.c:1248
       kernfs_fop_write_iter+0x375/0x4f0 fs/kernfs/file.c:334
       iter_file_splice_write+0x937/0x1000 fs/splice.c:738
       do_splice_from fs/splice.c:935 [inline]
       direct_splice_actor+0xfe/0x160 fs/splice.c:1158
       splice_direct_to_actor+0x5a5/0xcc0 fs/splice.c:1102
       do_splice_direct_actor fs/splice.c:1201 [inline]
       do_splice_direct+0x181/0x270 fs/splice.c:1227
       do_sendfile+0x4da/0x7d0 fs/read_write.c:1368
       __do_sys_sendfile64 fs/read_write.c:1429 [inline]
       __se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1415
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&of->mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
       kernfs_seq_start+0x55/0x3c0 fs/kernfs/file.c:154
       seq_read_iter+0x3ef/0xe10 fs/seq_file.c:225
       copy_splice_read+0x54f/0x9b0 fs/splice.c:363
       do_splice_read fs/splice.c:979 [inline]
       splice_direct_to_actor+0x4a6/0xcc0 fs/splice.c:1083
       do_splice_direct_actor fs/splice.c:1201 [inline]
       do_splice_direct+0x181/0x270 fs/splice.c:1227
       do_sendfile+0x4da/0x7d0 fs/read_write.c:1368
       __do_sys_sendfile64 fs/read_write.c:1429 [inline]
       __se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1415
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&p->lock){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
       seq_read_iter+0xb7/0xe10 fs/seq_file.c:182
       copy_splice_read+0x54f/0x9b0 fs/splice.c:363
       do_splice_read fs/splice.c:979 [inline]
       splice_file_to_pipe+0x270/0x440 fs/splice.c:1289
       do_sendfile+0x475/0x7d0 fs/read_write.c:1374
       __do_sys_sendfile64 fs/read_write.c:1429 [inline]
       __se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1415
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 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:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
       __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
       __mutex_lock_common kernel/locking/mutex.c:601 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
       iter_file_splice_write+0x1e6/0x1000 fs/splice.c:683
       do_splice_from fs/splice.c:935 [inline]
       do_splice+0xc76/0x1660 fs/splice.c:1348
       __do_splice fs/splice.c:1430 [inline]
       __do_sys_splice fs/splice.c:1633 [inline]
       __se_sys_splice+0x2e1/0x460 fs/splice.c:1615
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xf6/0x210 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#5

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_writers#5);
                               lock(&ovl_i_mutex_dir_key[depth]#2);
                               lock(sb_writers#5);
  lock(&pipe->mutex);

 *** DEADLOCK ***

1 lock held by syz.9.1492/22135:
 #0: ffff88805bc52420 (sb_writers#5){.+.+}-{0:0}, at: do_splice+0xbff/0x1660 fs/splice.c:1347

stack backtrace:
CPU: 1 UID: 0 PID: 22135 Comm: syz.9.1492 Not tainted 6.15.0-rc3-syzkaller-00342-g5bc1018675ec #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2079
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3909
 __lock_acquire+0xaac/0xd20 kernel/locking/lockdep.c:5235
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5866
 __mutex_lock_common kernel/locking/mutex.c:601 [inline]
 __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:746
 iter_file_splice_write+0x1e6/0x1000 fs/splice.c:683
 do_splice_from fs/splice.c:935 [inline]
 do_splice+0xc76/0x1660 fs/splice.c:1348
 __do_splice fs/splice.c:1430 [inline]
 __do_sys_splice fs/splice.c:1633 [inline]
 __se_sys_splice+0x2e1/0x460 fs/splice.c:1615
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f0c1418e969
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:00007f0c14f8e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f0c143b5fa0 RCX: 00007f0c1418e969
RDX: 0000000000000008 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f0c14210ab1 R08: 0000000800000008 R09: 0000000000000008
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f0c143b5fa0 R15: 00007ffd4f1385f8
 </TASK>