syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc5-syzkaller-00043-gd76bb1ebb558 #0 Not tainted
------------------------------------------------------
syz.2.4533/21669 is trying to acquire lock:
ffff88805b921888 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:877 [inline]
ffff88805b921888 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1833

but task is already holding lock:
ffff88802f779888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&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
       traverse+0x15c/0x570 fs/seq_file.c:106
       seq_read_iter+0xcfe/0xe10 fs/seq_file.c:195
       do_iter_readv_writev+0x56b/0x7f0 fs/read_write.c:-1
       vfs_readv+0x257/0x840 fs/read_write.c:1016
       do_preadv fs/read_write.c:1130 [inline]
       __do_sys_preadv fs/read_write.c:1177 [inline]
       __se_sys_preadv fs/read_write.c:1172 [inline]
       __x64_sys_preadv+0x197/0x2a0 fs/read_write.c:1172
       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 (&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
       proc_reg_read_iter+0x1b4/0x280 fs/proc/inode.c:299
       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

-> #2 (&pipe->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
       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

-> #1 (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_create_object+0xfc/0x310 fs/overlayfs/dir.c:628
       lookup_open fs/namei.c:3701 [inline]
       open_last_lookups fs/namei.c:3800 [inline]
       path_openat+0x14f1/0x3830 fs/namei.c:4036
       do_filp_open+0x1fa/0x410 fs/namei.c:4066
       do_sys_openat2+0x121/0x1c0 fs/open.c:1429
       do_sys_open fs/open.c:1444 [inline]
       __do_sys_open fs/open.c:1452 [inline]
       __se_sys_open fs/open.c:1448 [inline]
       __x64_sys_open+0x11e/0x150 fs/open.c:1448
       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 (&ovl_i_mutex_dir_key[depth]){++++}-{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
       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
       new_sync_write fs/read_write.c:591 [inline]
       vfs_write+0x548/0xa90 fs/read_write.c:684
       ksys_write+0x145/0x250 fs/read_write.c:736
       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:
  &ovl_i_mutex_dir_key[depth] --> &p->lock --> &of->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&of->mutex);
                               lock(&p->lock);
                               lock(&of->mutex);
  rlock(&ovl_i_mutex_dir_key[depth]);

 *** DEADLOCK ***

4 locks held by syz.2.4533/21669:
 #0: ffff888011894638 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1213
 #1: ffff88803540a420 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3041 [inline]
 #1: ffff88803540a420 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x211/0xa90 fs/read_write.c:680
 #2: ffff88802f779888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325
 #3: ffff8881416854b8 (kn->active#66){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x203/0x4f0 fs/kernfs/file.c:326

stack backtrace:
CPU: 1 UID: 0 PID: 21669 Comm: syz.2.4533 Not tainted 6.15.0-rc5-syzkaller-00043-gd76bb1ebb558 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/29/2025
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
 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
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x548/0xa90 fs/read_write.c:684
 ksys_write+0x145/0x250 fs/read_write.c:736
 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: 0033:0x7f91c578e969
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:00007f91c660a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f91c59b6160 RCX: 00007f91c578e969
RDX: 0000000000000012 RSI: 0000200000000040 RDI: 000000000000000b
RBP: 00007f91c5810ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f91c59b6160 R15: 00007fff7e2fd5a8
 </TASK>
PM: Image not found (code -22)