syzbot

======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc3-syzkaller-00072-gee88bddf7f2f #0 Not tainted
------------------------------------------------------
syz.4.1661/13688 is trying to acquire lock:
ffff8880589c3570 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:884 [inline]
ffff8880589c3570 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: lookup_slow+0x46/0x70 fs/namei.c:1833

but task is already holding lock:
ffff88805ac1ac88 (&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:

-> #2 (&of->mutex){+.+.}-{4:4}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
       __mutex_lock_common kernel/locking/mutex.c:602 [inline]
       __mutex_lock+0x182/0xe80 kernel/locking/mutex.c:747
       kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x54b/0xa90 fs/read_write.c:686
       ksys_write+0x145/0x250 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (sb_writers#9){.+.+}-{0:0}:
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
       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.h:1795 [inline]
       sb_start_write+0x4d/0x1c0 include/linux/fs.h:1931
       mnt_want_write+0x41/0x90 fs/namespace.c:557
       ovl_fix_origin fs/overlayfs/namei.c:908 [inline]
       ovl_lookup+0xaf6/0x1bc0 fs/overlayfs/namei.c:1168
       __lookup_slow+0x294/0x3d0 fs/namei.c:1817
       lookup_slow+0x53/0x70 fs/namei.c:1834
       walk_component fs/namei.c:2138 [inline]
       link_path_walk+0x935/0xea0 fs/namei.c:2506
       path_lookupat+0x97/0x430 fs/namei.c:2662
       filename_lookup+0x212/0x570 fs/namei.c:2692
       user_path_at+0x3a/0x60 fs/namei.c:3136
       __do_sys_chroot fs/open.c:603 [inline]
       __se_sys_chroot+0x90/0x3b0 fs/open.c:597
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0x3b0 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:3168 [inline]
       check_prevs_add kernel/locking/lockdep.c:3287 [inline]
       validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
       __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
       lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
       down_read+0x46/0x2e0 kernel/locking/rwsem.c:1524
       inode_lock_shared include/linux/fs.h:884 [inline]
       lookup_slow+0x46/0x70 fs/namei.c:1833
       walk_component+0x2d2/0x400 fs/namei.c:2138
       lookup_last fs/namei.c:2639 [inline]
       path_lookupat+0x163/0x430 fs/namei.c:2663
       filename_lookup+0x212/0x570 fs/namei.c:2692
       kern_path+0x35/0x50 fs/namei.c:2825
       lookup_bdev+0xc0/0x280 block/bdev.c:1205
       resume_store+0x169/0x460 kernel/power/hibernate.c:1272
       kernfs_fop_write_iter+0x375/0x4f0 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x54b/0xa90 fs/read_write.c:686
       ksys_write+0x145/0x250 fs/read_write.c:738
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xfa/0x3b0 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] --> sb_writers#9 --> &of->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&of->mutex);
                               lock(sb_writers#9);
                               lock(&of->mutex);
  rlock(&ovl_i_mutex_dir_key[depth]);

 *** DEADLOCK ***

4 locks held by syz.4.1661/13688:
 #0: ffff8880301809b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1217
 #1: ffff888035442428 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3096 [inline]
 #1: ffff888035442428 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x211/0xa90 fs/read_write.c:682
 #2: ffff88805ac1ac88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1e0/0x4f0 fs/kernfs/file.c:325
 #3: ffff888140ae6c38 (kn->active#62){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x203/0x4f0 fs/kernfs/file.c:326

stack backtrace:
CPU: 0 UID: 0 PID: 13688 Comm: syz.4.1661 Not tainted 6.16.0-rc3-syzkaller-00072-gee88bddf7f2f #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046
 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178
 check_prev_add kernel/locking/lockdep.c:3168 [inline]
 check_prevs_add kernel/locking/lockdep.c:3287 [inline]
 validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871
 down_read+0x46/0x2e0 kernel/locking/rwsem.c:1524
 inode_lock_shared include/linux/fs.h:884 [inline]
 lookup_slow+0x46/0x70 fs/namei.c:1833
 walk_component+0x2d2/0x400 fs/namei.c:2138
 lookup_last fs/namei.c:2639 [inline]
 path_lookupat+0x163/0x430 fs/namei.c:2663
 filename_lookup+0x212/0x570 fs/namei.c:2692
 kern_path+0x35/0x50 fs/namei.c:2825
 lookup_bdev+0xc0/0x280 block/bdev.c:1205
 resume_store+0x169/0x460 kernel/power/hibernate.c:1272
 kernfs_fop_write_iter+0x375/0x4f0 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x54b/0xa90 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f703138e929
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:00007f70321a5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f70315b6080 RCX: 00007f703138e929
RDX: 0000000000001006 RSI: 0000200000000500 RDI: 0000000000000003
RBP: 00007f7031410b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f70315b6080 R15: 00007ffe28e5ad78
 </TASK>