syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.3.2863/16700 is trying to acquire lock:
ffff8880591cba98 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:1042 [inline]
ffff8880591cba98 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: lookup_slow+0x42/0x70 fs/namei.c:1874

but task is already holding lock:
ffff88802ae1b088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x570 fs/kernfs/file.c:343

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&of->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1aa/0x1b10 kernel/locking/mutex.c:776
       kernfs_seq_start+0x4f/0x2a0 fs/kernfs/file.c:172
       traverse.part.0.constprop.0+0xaf/0x650 fs/seq_file.c:106
       traverse fs/seq_file.c:98 [inline]
       seq_read_iter+0x93c/0x12d0 fs/seq_file.c:195
       kernfs_fop_read_iter+0x46c/0x610 fs/kernfs/file.c:297
       lo_rw_aio.isra.0+0x9d5/0x1040 drivers/block/loop.c:406
       do_req_filebacked drivers/block/loop.c:437 [inline]
       loop_handle_cmd drivers/block/loop.c:1927 [inline]
       loop_process_work+0x8fc/0x1140 drivers/block/loop.c:1962
       process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
       process_scheduled_works kernel/workqueue.c:3340 [inline]
       worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
       kthread+0x3c5/0x780 kernel/kthread.c:463
       ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

-> #3 (&p->lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1aa/0x1b10 kernel/locking/mutex.c:776
       seq_read_iter+0xe1/0x12d0 fs/seq_file.c:182
       kernfs_fop_read_iter+0x46c/0x610 fs/kernfs/file.c:297
       copy_splice_read+0x618/0xc20 fs/splice.c:363
       do_splice_read fs/splice.c:982 [inline]
       do_splice_read+0x285/0x370 fs/splice.c:956
       splice_file_to_pipe+0x109/0x120 fs/splice.c:1292
       do_sendfile+0x400/0xe50 fs/read_write.c:1376
       __do_sys_sendfile64 fs/read_write.c:1431 [inline]
       __se_sys_sendfile64 fs/read_write.c:1417 [inline]
       __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1417
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&pipe->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1aa/0x1b10 kernel/locking/mutex.c:776
       pipe_lock fs/pipe.c:91 [inline]
       pipe_lock+0x64/0x80 fs/pipe.c:88
       iter_file_splice_write+0x1ea/0x12b0 fs/splice.c:683
       do_splice_from fs/splice.c:938 [inline]
       do_splice+0x1478/0x1fc0 fs/splice.c:1351
       __do_splice+0x32a/0x360 fs/splice.c:1433
       __do_sys_splice fs/splice.c:1636 [inline]
       __se_sys_splice fs/splice.c:1618 [inline]
       __x64_sys_splice+0x187/0x250 fs/splice.c:1618
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (sb_writers#6){.+.+}-{0:0}:
       percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
       percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
       __sb_start_write include/linux/fs/super.h:19 [inline]
       sb_start_write include/linux/fs/super.h:125 [inline]
       mnt_want_write+0x6f/0x450 fs/namespace.c:499
       ovl_create_object+0x12b/0x3b0 fs/overlayfs/dir.c:691
       lookup_open.isra.0+0x12dc/0x1780 fs/namei.c:4440
       open_last_lookups fs/namei.c:4540 [inline]
       path_openat+0xa95/0x3140 fs/namei.c:4784
       do_filp_open+0x20b/0x470 fs/namei.c:4814
       do_sys_openat2+0x11f/0x280 fs/open.c:1430
       do_sys_open fs/open.c:1436 [inline]
       __do_sys_openat fs/open.c:1452 [inline]
       __se_sys_openat fs/open.c:1447 [inline]
       __x64_sys_openat+0x174/0x210 fs/open.c:1447
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0xf80 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:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1542/0x22f0 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825
       down_read+0x9b/0x460 kernel/locking/rwsem.c:1537
       inode_lock_shared include/linux/fs.h:1042 [inline]
       lookup_slow+0x42/0x70 fs/namei.c:1874
       walk_component fs/namei.c:2221 [inline]
       lookup_last fs/namei.c:2722 [inline]
       path_lookupat+0x5e9/0xc40 fs/namei.c:2746
       filename_lookup+0x224/0x5f0 fs/namei.c:2775
       kern_path+0x35/0x50 fs/namei.c:2987
       lookup_bdev+0xd8/0x280 block/bdev.c:1222
       resume_store+0x1d6/0x460 kernel/power/hibernate.c:1306
       kobj_attr_store+0x58/0x80 lib/kobject.c:840
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142
       kernfs_fop_write_iter+0x3af/0x570 fs/kernfs/file.c:352
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x7d3/0x11d0 fs/read_write.c:686
       ksys_write+0x12a/0x250 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0xf80 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.3.2863/16700:
 #0: ffff888035ef7eb8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1255
 #1: ffff888036710420 (sb_writers#8){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:738
 #2: ffff88802ae1b088 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x570 fs/kernfs/file.c:343
 #3: ffff888140e84878 (kn->active#80){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #3: ffff888140e84878 (kn->active#80){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2ff/0x570 fs/kernfs/file.c:344

stack backtrace:
CPU: 1 UID: 0 PID: 16700 Comm: syz.3.2863 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x2db/0x410 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1542/0x22f0 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825
 down_read+0x9b/0x460 kernel/locking/rwsem.c:1537
 inode_lock_shared include/linux/fs.h:1042 [inline]
 lookup_slow+0x42/0x70 fs/namei.c:1874
 walk_component fs/namei.c:2221 [inline]
 lookup_last fs/namei.c:2722 [inline]
 path_lookupat+0x5e9/0xc40 fs/namei.c:2746
 filename_lookup+0x224/0x5f0 fs/namei.c:2775
 kern_path+0x35/0x50 fs/namei.c:2987
 lookup_bdev+0xd8/0x280 block/bdev.c:1222
 resume_store+0x1d6/0x460 kernel/power/hibernate.c:1306
 kobj_attr_store+0x58/0x80 lib/kobject.c:840
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142
 kernfs_fop_write_iter+0x3af/0x570 fs/kernfs/file.c:352
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x7d3/0x11d0 fs/read_write.c:686
 ksys_write+0x12a/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f423ab8f749
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:00007f423ba7f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f423ade6090 RCX: 00007f423ab8f749
RDX: 0000000000000012 RSI: 0000200000000040 RDI: 0000000000000007
RBP: 00007f423ac13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f423ade6128 R14: 00007f423ade6090 R15: 00007ffe290993e8
 </TASK>
PM: Image not found (code -22)