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Date: Mon, 08 Apr 2024 04:49:28 -0700
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Subject: [syzbot] [kernfs?] possible deadlock in lookup_one_unlocked
From: syzbot <syzbot+ac3c5eb32b9d409dc11d@syzkaller.appspotmail.com>
To: gregkh@linuxfoundation.org, linux-fsdevel@vger.kernel.org, 
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tj@kernel.org
Content-Type: text/plain; charset="UTF-8"

Hello,

syzbot found the following issue on:

HEAD commit:    fe46a7dd189e Merge tag 'sound-6.9-rc1' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17adb6d3180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4d90a36f0cab495a
dashboard link: https://syzkaller.appspot.com/bug?extid=ac3c5eb32b9d409dc11d
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/72ab73815344/disk-fe46a7dd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2d6d6b0d7071/vmlinux-fe46a7dd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/48e275e5478b/bzImage-fe46a7dd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ac3c5eb32b9d409dc11d@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
6.8.0-syzkaller-08951-gfe46a7dd189e #0 Not tainted
------------------------------------------------------
syz-executor.1/9023 is trying to acquire lock:
ffff88805d610740 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:803 [inline]
ffff88805d610740 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_slow fs/namei.c:1708 [inline]
ffff88805d610740 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: lookup_one_unlocked+0x197/0x290 fs/namei.c:2817

but task is already holding lock:
ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: inode_lock_shared include/linux/fs.h:803 [inline]
ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: lookup_slow+0x45/0x70 fs/namei.c:1708

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
       inode_lock_shared include/linux/fs.h:803 [inline]
       lookup_slow+0x45/0x70 fs/namei.c:1708
       walk_component+0x2e1/0x410 fs/namei.c:2004
       lookup_last fs/namei.c:2461 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2485
       filename_lookup+0x256/0x610 fs/namei.c:2514
       kern_path+0x35/0x50 fs/namei.c:2622
       lookup_bdev+0xc5/0x290 block/bdev.c:1072
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
       kernfs_fop_write_iter+0x3a4/0x500 fs/kernfs/file.c:334
       call_write_iter include/linux/fs.h:2108 [inline]
       new_sync_write fs/read_write.c:497 [inline]
       vfs_write+0xa84/0xcb0 fs/read_write.c:590
       ksys_write+0x1a0/0x2c0 fs/read_write.c:643
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #4 (&of->mutex){+.+.}-{3:3}:
       lock_acquire+0x1e4/0x530 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
       call_read_iter include/linux/fs.h:2102 [inline]
       new_sync_read fs/read_write.c:395 [inline]
       vfs_read+0x97b/0xb70 fs/read_write.c:476
       ksys_read+0x1a0/0x2c0 fs/read_write.c:619
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #3 (&p->lock){+.+.}-{3:3}:
       lock_acquire+0x1e4/0x530 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
       call_read_iter include/linux/fs.h:2102 [inline]
       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+0x515/0xdc0 fs/read_write.c:1301
       __do_sys_sendfile64 fs/read_write.c:1362 [inline]
       __se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #2 (&pipe->mutex){+.+.}-{3:3}:
       lock_acquire+0x1e4/0x530 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+0xd77/0x1880 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_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #1 (sb_writers#4){.+.+}-{0:0}:
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1662 [inline]
       sb_start_write+0x4d/0x1c0 include/linux/fs.h:1798
       mnt_want_write+0x3f/0x90 fs/namespace.c:409
       ovl_create_object+0x13b/0x370 fs/overlayfs/dir.c:629
       lookup_open fs/namei.c:3497 [inline]
       open_last_lookups fs/namei.c:3566 [inline]
       path_openat+0x1425/0x3240 fs/namei.c:3796
       do_filp_open+0x235/0x490 fs/namei.c:3826
       do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
       do_sys_open fs/open.c:1421 [inline]
       __do_sys_open fs/open.c:1429 [inline]
       __se_sys_open fs/open.c:1425 [inline]
       __x64_sys_open+0x225/0x270 fs/open.c:1425
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

-> #0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
       __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
       lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
       down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
       inode_lock_shared include/linux/fs.h:803 [inline]
       lookup_slow fs/namei.c:1708 [inline]
       lookup_one_unlocked+0x197/0x290 fs/namei.c:2817
       ovl_lookup_positive_unlocked fs/overlayfs/namei.c:210 [inline]
       ovl_lookup_single+0x200/0xbd0 fs/overlayfs/namei.c:240
       ovl_lookup_layer+0x417/0x510 fs/overlayfs/namei.c:333
       ovl_lookup+0xcf7/0x2a60 fs/overlayfs/namei.c:1124
       __lookup_slow+0x28c/0x3f0 fs/namei.c:1692
       lookup_slow+0x53/0x70 fs/namei.c:1709
       walk_component+0x2e1/0x410 fs/namei.c:2004
       lookup_last fs/namei.c:2461 [inline]
       path_lookupat+0x16f/0x450 fs/namei.c:2485
       filename_lookup+0x256/0x610 fs/namei.c:2514
       kern_path+0x35/0x50 fs/namei.c:2622
       lookup_bdev+0xc5/0x290 block/bdev.c:1072
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
       kernfs_fop_write_iter+0x3a4/0x500 fs/kernfs/file.c:334
       call_write_iter include/linux/fs.h:2108 [inline]
       new_sync_write fs/read_write.c:497 [inline]
       vfs_write+0xa84/0xcb0 fs/read_write.c:590
       ksys_write+0x1a0/0x2c0 fs/read_write.c:643
       do_syscall_64+0xfb/0x240
       entry_SYSCALL_64_after_hwframe+0x6d/0x75

other info that might help us debug this:

Chain exists of:
  &ovl_i_mutex_dir_key[depth] --> &of->mutex --> &ovl_i_mutex_dir_key[depth]#3

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&ovl_i_mutex_dir_key[depth]#3);
                               lock(&of->mutex);
                               lock(&ovl_i_mutex_dir_key[depth]#3);
  rlock(&ovl_i_mutex_dir_key[depth]);

 *** DEADLOCK ***

5 locks held by syz-executor.1/9023:
 #0: ffff888059ebf248 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x259/0x320 fs/file.c:1191
 #1: ffff88802f972420 (sb_writers#8){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2853 [inline]
 #1: ffff88802f972420 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x233/0xcb0 fs/read_write.c:586
 #2: ffff88801edfd088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1eb/0x500 fs/kernfs/file.c:325
 #3: ffff888019281918 (kn->active#59){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x20f/0x500 fs/kernfs/file.c:326
 #4: ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: inode_lock_shared include/linux/fs.h:803 [inline]
 #4: ffff88805d612450 (&ovl_i_mutex_dir_key[depth]#3){.+.+}-{3:3}, at: lookup_slow+0x45/0x70 fs/namei.c:1708

stack backtrace:
CPU: 1 PID: 9023 Comm: syz-executor.1 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
 lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754
 down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
 inode_lock_shared include/linux/fs.h:803 [inline]
 lookup_slow fs/namei.c:1708 [inline]
 lookup_one_unlocked+0x197/0x290 fs/namei.c:2817
 ovl_lookup_positive_unlocked fs/overlayfs/namei.c:210 [inline]
 ovl_lookup_single+0x200/0xbd0 fs/overlayfs/namei.c:240
 ovl_lookup_layer+0x417/0x510 fs/overlayfs/namei.c:333
 ovl_lookup+0xcf7/0x2a60 fs/overlayfs/namei.c:1124
 __lookup_slow+0x28c/0x3f0 fs/namei.c:1692
 lookup_slow+0x53/0x70 fs/namei.c:1709
 walk_component+0x2e1/0x410 fs/namei.c:2004
 lookup_last fs/namei.c:2461 [inline]
 path_lookupat+0x16f/0x450 fs/namei.c:2485
 filename_lookup+0x256/0x610 fs/namei.c:2514
 kern_path+0x35/0x50 fs/namei.c:2622
 lookup_bdev+0xc5/0x290 block/bdev.c:1072
 resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
 kernfs_fop_write_iter+0x3a4/0x500 fs/kernfs/file.c:334
 call_write_iter include/linux/fs.h:2108 [inline]
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xa84/0xcb0 fs/read_write.c:590
 ksys_write+0x1a0/0x2c0 fs/read_write.c:643
 do_syscall_64+0xfb/0x240
 entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f389687de69
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:00007f38963ff0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f38969abf80 RCX: 00007f389687de69
RDX: 0000000000000012 RSI: 0000000020000000 RDI: 0000000000000006
RBP: 00007f38968ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f38969abf80 R15: 00007ffca27d9338
 </TASK>
PM: Image not found (code -6)


---
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