syzbot

netlink: 20 bytes leftover after parsing attributes in process `syz.3.3856'.
======================================================
WARNING: possible circular locking dependency detected
6.14.0-rc6-syzkaller-00145-g695caca9345a #0 Not tainted
------------------------------------------------------
syz.3.3856/20452 is trying to acquire lock:
ffff88805cbc4100 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: inode_lock_shared include/linux/fs.h:887 [inline]
ffff88805cbc4100 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}, at: lookup_slow+0x45/0x70 fs/namei.c:1809

but task is already holding lock:
ffff88806b6ec888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&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+0xbfa/0x1510 fs/splice.c:743
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd68/0x18b0 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

-> #2 (&pipe->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
       iter_file_splice_write+0x330/0x1510 fs/splice.c:687
       backing_file_splice_write+0x35f/0x580 fs/backing-file.c:315
       ovl_splice_write+0x4b8/0x630 fs/overlayfs/file.c:440
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd68/0x18b0 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

-> #1 (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+0x4d/0x1c0 include/linux/fs.h:1921
       mnt_want_write+0x3f/0x90 fs/namespace.c:547
       ovl_create_object+0x13a/0x3a0 fs/overlayfs/dir.c:656
       lookup_open fs/namei.c:3651 [inline]
       open_last_lookups fs/namei.c:3750 [inline]
       path_openat+0x193c/0x3590 fs/namei.c:3986
       do_filp_open+0x27f/0x4e0 fs/namei.c:4016
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1428
       do_sys_open fs/open.c:1443 [inline]
       __do_sys_openat fs/open.c:1459 [inline]
       __se_sys_openat fs/open.c:1454 [inline]
       __x64_sys_openat+0x247/0x2a0 fs/open.c:1454
       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 (&ovl_i_mutex_dir_key[depth]){++++}-{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
       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+0x3a0/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:586 [inline]
       vfs_write+0xacf/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

other info that might help us debug this:

Chain exists of:
  &ovl_i_mutex_dir_key[depth] --> &pipe->mutex --> &of->mutex

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

4 locks held by syz.3.3856/20452:
 #0: ffff8880695c9cf8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x254/0x320 fs/file.c:1192
 #1: ffff8880240b6420 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3035 [inline]
 #1: ffff8880240b6420 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x225/0xd10 fs/read_write.c:675
 #2: ffff88806b6ec888 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1ea/0x500 fs/kernfs/file.c:325
 #3: ffff888142292008 (kn->active#56){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20e/0x500 fs/kernfs/file.c:326

stack backtrace:
CPU: 0 UID: 0 PID: 20452 Comm: syz.3.3856 Not tainted 6.14.0-rc6-syzkaller-00145-g695caca9345a #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
 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+0x3a0/0x500 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0xacf/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
RIP: 0033:0x7ff87a98d169
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:00007ff87b74d038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ff87aba6080 RCX: 00007ff87a98d169
RDX: 0000000000000012 RSI: 0000400000000040 RDI: 0000000000000004
RBP: 00007ff87aa0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007ff87aba6080 R15: 00007fffc7bfbe78
 </TASK>
block device autoloading is deprecated and will be removed.
PM: Image not found (code -22)