syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.5.2442/15313 is trying to acquire lock:
ffff888056a22790 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xe1/0x1270 fs/seq_file.c:182

but task is already holding lock:
ffff888056e00868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline]
ffff888056e00868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x69/0x80 fs/pipe.c:88

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&pipe->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       pipe_lock fs/pipe.c:91 [inline]
       pipe_lock+0x69/0x80 fs/pipe.c:88
       iter_file_splice_write+0x1f8/0x10a0 fs/splice.c:683
       do_splice_from fs/splice.c:938 [inline]
       do_splice+0x109c/0x1fd0 fs/splice.c:1351
       __do_splice+0x33b/0x370 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+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (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_fileattr_set+0x108/0x300 fs/overlayfs/inode.c:646
       vfs_fileattr_set+0x783/0xd70 fs/file_attr.c:299
       ioctl_setflags+0x1c7/0x200 fs/file_attr.c:335
       do_vfs_ioctl+0x705/0x13e0 fs/ioctl.c:560
       __do_sys_ioctl fs/ioctl.c:595 [inline]
       __se_sys_ioctl fs/ioctl.c:583 [inline]
       __x64_sys_ioctl+0x114/0x210 fs/ioctl.c:583
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&ovl_i_mutex_dir_key[depth]#2){++++}-{4:4}:
       down_read+0x99/0x460 kernel/locking/rwsem.c:1537
       inode_lock_shared include/linux/fs.h:1042 [inline]
       lookup_slow+0x42/0x70 fs/namei.c:1882
       walk_component fs/namei.c:2229 [inline]
       link_path_walk+0x1377/0x1cc0 fs/namei.c:2597
       path_lookupat+0x74/0xc40 fs/namei.c:2753
       filename_lookup+0x202/0x590 fs/namei.c:2783
       kern_path+0x35/0x50 fs/namei.c:2996
       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+0x3e0/0x5f0 fs/kernfs/file.c:352
       iter_file_splice_write+0x82b/0x10a0 fs/splice.c:738
       do_splice_from fs/splice.c:938 [inline]
       direct_splice_actor+0x192/0x6c0 fs/splice.c:1161
       splice_direct_to_actor+0x345/0xa30 fs/splice.c:1105
       do_splice_direct_actor fs/splice.c:1204 [inline]
       do_splice_direct+0x174/0x240 fs/splice.c:1230
       do_sendfile+0xadc/0xe20 fs/read_write.c:1370
       __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+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&of->mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       kernfs_seq_start+0x4f/0x2a0 fs/kernfs/file.c:172
       seq_read_iter+0x2c1/0x1270 fs/seq_file.c:225
       kernfs_fop_read_iter+0x46c/0x610 fs/kernfs/file.c:297
       copy_splice_read+0x4ba/0xb90 fs/splice.c:363
       do_splice_read fs/splice.c:982 [inline]
       do_splice_read+0x285/0x370 fs/splice.c:956
       splice_direct_to_actor+0x2a1/0xa30 fs/splice.c:1086
       do_splice_direct_actor fs/splice.c:1204 [inline]
       do_splice_direct+0x174/0x240 fs/splice.c:1230
       do_sendfile+0xadc/0xe20 fs/read_write.c:1370
       __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+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&p->lock){+.+.}-{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+0x14b8/0x2630 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x17c/0x330 kernel/locking/lockdep.c:5825
       __mutex_lock_common kernel/locking/mutex.c:614 [inline]
       __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
       seq_read_iter+0xe1/0x1270 fs/seq_file.c:182
       kernfs_fop_read_iter+0x46c/0x610 fs/kernfs/file.c:297
       copy_splice_read+0x4ba/0xb90 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+0x82/0x120 fs/splice.c:1292
       do_sendfile+0x366/0xe20 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+0xc9/0xf80 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:
  &p->lock --> sb_writers#6 --> &pipe->mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&pipe->mutex);
                               lock(sb_writers#6);
                               lock(&pipe->mutex);
  lock(&p->lock);

 *** DEADLOCK ***

1 lock held by syz.5.2442/15313:
 #0: ffff888056e00868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline]
 #0: ffff888056e00868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x69/0x80 fs/pipe.c:88

stack backtrace:
CPU: 0 UID: 0 PID: 15313 Comm: syz.5.2442 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 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+0x14b8/0x2630 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x17c/0x330 kernel/locking/lockdep.c:5825
 __mutex_lock_common kernel/locking/mutex.c:614 [inline]
 __mutex_lock+0x1a2/0x1b90 kernel/locking/mutex.c:776
 seq_read_iter+0xe1/0x1270 fs/seq_file.c:182
 kernfs_fop_read_iter+0x46c/0x610 fs/kernfs/file.c:297
 copy_splice_read+0x4ba/0xb90 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+0x82/0x120 fs/splice.c:1292
 do_sendfile+0x366/0xe20 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+0xc9/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa8ce99aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa8cf7d8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fa8cec15fa0 RCX: 00007fa8ce99aeb9
RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000000
RBP: 00007fa8cea08c1f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa8cec16038 R14: 00007fa8cec15fa0 R15: 00007fff93576da8
 </TASK>