syzbot

======================================================
WARNING: possible circular locking dependency detected
6.16.0-rc7-syzkaller-00140-gec2df4364666 #0 Not tainted
------------------------------------------------------
syz.1.4419/22764 is trying to acquire lock:
ffff8880262b3c30 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xe1/0x12c0 fs/seq_file.c:182

but task is already holding lock:
ffff88804ee60c68 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline]
ffff88804ee60c68 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x64/0x80 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:602 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
       pipe_lock fs/pipe.c:91 [inline]
       pipe_lock+0x64/0x80 fs/pipe.c:88
       iter_file_splice_write+0x1ea/0x1150 fs/splice.c:683
       do_splice_from fs/splice.c:935 [inline]
       do_splice+0x1478/0x1fc0 fs/splice.c:1348
       __do_splice+0x27d/0x360 fs/splice.c:1430
       __do_sys_splice fs/splice.c:1633 [inline]
       __se_sys_splice fs/splice.c:1615 [inline]
       __x64_sys_splice+0x187/0x250 fs/splice.c:1615
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 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.h:1795 [inline]
       sb_start_write include/linux/fs.h:1931 [inline]
       mnt_want_write+0x6f/0x450 fs/namespace.c:557
       ovl_create_object+0x12c/0x300 fs/overlayfs/dir.c:628
       lookup_open.isra.0+0x11d3/0x1580 fs/namei.c:3717
       open_last_lookups fs/namei.c:3816 [inline]
       path_openat+0x893/0x2cb0 fs/namei.c:4052
       do_filp_open+0x20b/0x470 fs/namei.c:4082
       do_sys_openat2+0x11b/0x1d0 fs/open.c:1437
       do_sys_open fs/open.c:1452 [inline]
       __do_sys_creat fs/open.c:1530 [inline]
       __se_sys_creat fs/open.c:1524 [inline]
       __x64_sys_creat+0xcc/0x120 fs/open.c:1524
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&ovl_i_mutex_dir_key[depth]){++++}-{4:4}:
       down_read+0x9b/0x480 kernel/locking/rwsem.c:1524
       inode_lock_shared include/linux/fs.h:884 [inline]
       lookup_slow fs/namei.c:1833 [inline]
       walk_component+0x345/0x5b0 fs/namei.c:2138
       lookup_last fs/namei.c:2639 [inline]
       path_lookupat+0x142/0x6d0 fs/namei.c:2663
       filename_lookup+0x224/0x5f0 fs/namei.c:2692
       kern_path+0x35/0x50 fs/namei.c:2825
       lookup_bdev+0xd8/0x280 block/bdev.c:1205
       resume_store+0x1d6/0x460 kernel/power/hibernate.c:1269
       kobj_attr_store+0x55/0x80 lib/kobject.c:840
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:593 [inline]
       vfs_write+0x6c4/0x1150 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/0x4c0 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:602 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
       kernfs_seq_start+0x4d/0x240 fs/kernfs/file.c:154
       seq_read_iter+0x2c1/0x12c0 fs/seq_file.c:225
       kernfs_fop_read_iter+0x40f/0x5a0 fs/kernfs/file.c:279
       copy_splice_read+0x618/0xba0 fs/splice.c:363
       do_splice_read fs/splice.c:979 [inline]
       do_splice_read+0x282/0x370 fs/splice.c:953
       splice_direct_to_actor+0x2a1/0xa30 fs/splice.c:1083
       do_splice_direct_actor fs/splice.c:1201 [inline]
       do_splice_direct+0x174/0x240 fs/splice.c:1227
       do_sendfile+0xb06/0xe50 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+0xcd/0x4c0 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:3168 [inline]
       check_prevs_add kernel/locking/lockdep.c:3287 [inline]
       validate_chain kernel/locking/lockdep.c:3911 [inline]
       __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
       lock_acquire kernel/locking/lockdep.c:5871 [inline]
       lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
       __mutex_lock_common kernel/locking/mutex.c:602 [inline]
       __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
       seq_read_iter+0xe1/0x12c0 fs/seq_file.c:182
       proc_reg_read_iter+0x21d/0x310 fs/proc/inode.c:299
       copy_splice_read+0x618/0xba0 fs/splice.c:363
       do_splice_read fs/splice.c:979 [inline]
       do_splice_read+0x282/0x370 fs/splice.c:953
       splice_file_to_pipe+0x109/0x120 fs/splice.c:1289
       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/0x4c0 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.1.4419/22764:
 #0: ffff88804ee60c68 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline]
 #0: ffff88804ee60c68 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x64/0x80 fs/pipe.c:88

stack backtrace:
CPU: 1 UID: 0 PID: 22764 Comm: syz.1.4419 Not tainted 6.16.0-rc7-syzkaller-00140-gec2df4364666 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2046
 check_noncircular+0x14c/0x170 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 kernel/locking/lockdep.c:3911 [inline]
 __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5240
 lock_acquire kernel/locking/lockdep.c:5871 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5828
 __mutex_lock_common kernel/locking/mutex.c:602 [inline]
 __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:747
 seq_read_iter+0xe1/0x12c0 fs/seq_file.c:182
 proc_reg_read_iter+0x21d/0x310 fs/proc/inode.c:299
 copy_splice_read+0x618/0xba0 fs/splice.c:363
 do_splice_read fs/splice.c:979 [inline]
 do_splice_read+0x282/0x370 fs/splice.c:953
 splice_file_to_pipe+0x109/0x120 fs/splice.c:1289
 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/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9684d8e9a9
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:00007f9685bc8038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f9684fb5fa0 RCX: 00007f9684d8e9a9
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000007
RBP: 00007f9684e10d69 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9684fb5fa0 R15: 00007ffc635cdf18
 </TASK>