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Date: Tue, 04 Jun 2024 11:50:27 -0700
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Subject: [syzbot] [overlayfs?] possible deadlock in iter_file_splice_write (4)
From: syzbot <syzbot+5ce16f43e888965f009d@syzkaller.appspotmail.com>
To: amir73il@gmail.com, linux-kernel@vger.kernel.org, 
	linux-unionfs@vger.kernel.org, miklos@szeredi.hu, 
	syzkaller-bugs@googlegroups.com
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Hello,

syzbot found the following issue on:

HEAD commit:    f06ce441457d Merge tag 'loongarch-fixes-6.10-1' of git://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1435a032980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=eb72437243175f22
dashboard link: https://syzkaller.appspot.com/bug?extid=5ce16f43e888965f009d
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/00ecb7bdd1a8/disk-f06ce441.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3926ab949197/vmlinux-f06ce441.xz
kernel image: https://storage.googleapis.com/syzbot-assets/36849eea4fc5/bzImage-f06ce441.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5ce16f43e888965f009d@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.10.0-rc2-syzkaller-00007-gf06ce441457d #0 Not tainted
------------------------------------------------------
syz-executor.3/17052 is trying to acquire lock:
ffff888022903468 (&pipe->mutex){+.+.}-{3:3}, at: iter_file_splice_write+0x335/0x14e0 fs/splice.c:687

but task is already holding lock:
ffff8880292be420 (sb_writers#4){.+.+}-{0:0}, at: do_splice+0xcf0/0x1900 fs/splice.c:1353

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (sb_writers#4){.+.+}-{0:0}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1655 [inline]
       sb_start_write+0x4d/0x1c0 include/linux/fs.h:1791
       mnt_want_write+0x3f/0x90 fs/namespace.c:409
       ovl_create_object+0x13b/0x370 fs/overlayfs/dir.c:642
       lookup_open fs/namei.c:3505 [inline]
       open_last_lookups fs/namei.c:3574 [inline]
       path_openat+0x1425/0x3280 fs/namei.c:3804
       do_filp_open+0x235/0x490 fs/namei.c:3834
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1405
       do_sys_open fs/open.c:1420 [inline]
       __do_sys_openat fs/open.c:1436 [inline]
       __se_sys_openat fs/open.c:1431 [inline]
       __x64_sys_openat+0x247/0x2a0 fs/open.c:1431
       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

-> #3 (&ovl_i_mutex_dir_key[depth]
){++++}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
       inode_lock_shared include/linux/fs.h:801 [inline]
       lookup_slow+0x45/0x70 fs/namei.c:1708
       walk_component+0x2e1/0x410 fs/namei.c:2004
       lookup_last fs/namei.c:2469 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2493
       filename_lookup+0x256/0x610 fs/namei.c:2522
       kern_path+0x35/0x50 fs/namei.c:2630
       lookup_bdev+0xc5/0x290 block/bdev.c:1157
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
       kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
       new_sync_write fs/read_write.c:497 [inline]
       vfs_write+0xa72/0xc90 fs/read_write.c:590
       ksys_write+0x1a0/0x2c0 fs/read_write.c:643
       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 (&of->mutex){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154
       seq_read_iter+0x3d0/0xd60 fs/seq_file.c:225
       do_iter_readv_writev+0x5a4/0x800
       vfs_readv+0x2b6/0xa90 fs/read_write.c:932
       do_preadv fs/read_write.c:1049 [inline]
       __do_sys_preadv fs/read_write.c:1099 [inline]
       __se_sys_preadv fs/read_write.c:1094 [inline]
       __x64_sys_preadv+0x1c7/0x2d0 fs/read_write.c:1094
       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 (&p->lock){+.+.}-{3:3}:
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
       copy_splice_read+0x662/0xb60 fs/splice.c:365
       do_splice_read fs/splice.c:985 [inline]
       splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
       do_sendfile+0x515/0xe10 fs/read_write.c:1301
       __do_sys_sendfile64 fs/read_write.c:1356 [inline]
       __se_sys_sendfile64+0x100/0x1e0 fs/read_write.c:1348
       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 (&pipe->mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:608 [inline]
       __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
       iter_file_splice_write+0x335/0x14e0 fs/splice.c:687
       do_splice_from fs/splice.c:941 [inline]
       do_splice+0xd77/0x1900 fs/splice.c:1354
       __do_splice fs/splice.c:1436 [inline]
       __do_sys_splice fs/splice.c:1652 [inline]
       __se_sys_splice+0x331/0x4a0 fs/splice.c:1634
       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:
  
&pipe->mutex --> &ovl_i_mutex_dir_key[depth] --> sb_writers#4

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(sb_writers#4);
                               lock(&ovl_i_mutex_dir_key[depth]);
                               lock(sb_writers#4);
  lock(&pipe->mutex);

 *** DEADLOCK ***

1 lock held by syz-executor.3/17052:
 #0: ffff8880292be420 (sb_writers#4){.+.+}-{0:0}, at: do_splice+0xcf0/0x1900 fs/splice.c:1353

stack backtrace:
CPU: 1 PID: 17052 Comm: syz-executor.3 Not tainted 6.10.0-rc2-syzkaller-00007-gf06ce441457d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:608 [inline]
 __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
 iter_file_splice_write+0x335/0x14e0 fs/splice.c:687
 do_splice_from fs/splice.c:941 [inline]
 do_splice+0xd77/0x1900 fs/splice.c:1354
 __do_splice fs/splice.c:1436 [inline]
 __do_sys_splice fs/splice.c:1652 [inline]
 __se_sys_splice+0x331/0x4a0 fs/splice.c:1634
 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: 0033:0x7f93d627cf69
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f93d5dde0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007f93d63b4070 RCX: 00007f93d627cf69
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f93d62da706 R08: 00000000ffffffe1 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f93d63b4070 R15: 00007ffc1c7ac468
 </TASK>


---
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