syzbot


possible deadlock in ovl_nlink_start

Status: closed as dup on 2024/04/19 07:03
Subsystems: overlayfs
[Documentation on labels]
Reported-by: syzbot+5ad5425056304cbce654@syzkaller.appspotmail.com
First crash: 222d, last: 196d
Duplicate of
Title Repro Cause bisect Fix bisect Count Last Reported
possible deadlock in kernfs_fop_llseek kernfs C done 38 222d 234d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [overlayfs?] possible deadlock in ovl_nlink_start 2 (3) 2024/04/21 00:21
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 possible deadlock in ovl_nlink_start 1 1446d 1446d 0/1 auto-closed as invalid on 2021/04/07 14:02
linux-4.14 possible deadlock in ovl_nlink_start (2) 1 820d 820d 0/1 auto-obsoleted due to no activity on 2022/12/24 15:21

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc7-syzkaller-00136-gf4345f05c0df #0 Not tainted
------------------------------------------------------
syz-executor.2/11429 is trying to acquire lock:
ffff88807a3e7968 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:654 [inline]
ffff88807a3e7968 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_nlink_start+0xdc/0x390 fs/overlayfs/util.c:1162

but task is already holding lock:
ffff88807a3e75b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock include/linux/fs.h:795 [inline]
ffff88807a3e75b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: vfs_rmdir+0x101/0x4c0 fs/namei.c:4195

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}:
       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:805 [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:1136
       resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
       kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
       call_write_iter include/linux/fs.h:2110 [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_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #4 (&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
       call_read_iter include/linux/fs.h:2104 [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_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&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
       call_read_iter include/linux/fs.h:2104 [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_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&pipe->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
       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_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (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:1664 [inline]
       sb_start_write include/linux/fs.h:1800 [inline]
       ovl_start_write+0x11d/0x290 fs/overlayfs/util.c:31
       ovl_do_copy_up fs/overlayfs/copy_up.c:967 [inline]
       ovl_copy_up_one fs/overlayfs/copy_up.c:1168 [inline]
       ovl_copy_up_flags+0x1105/0x4450 fs/overlayfs/copy_up.c:1223
       ovl_link+0x85/0x320 fs/overlayfs/dir.c:703
       vfs_link+0x4f5/0x690 fs/namei.c:4605
       do_linkat+0x356/0x760 fs/namei.c:4676
       __do_sys_linkat fs/namei.c:4704 [inline]
       __se_sys_linkat fs/namei.c:4701 [inline]
       __x64_sys_linkat+0xdd/0xf0 fs/namei.c:4701
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&ovl_i_lock_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+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
       ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:654 [inline]
       ovl_nlink_start+0xdc/0x390 fs/overlayfs/util.c:1162
       ovl_do_remove+0x1fa/0xd90 fs/overlayfs/dir.c:893
       vfs_rmdir+0x367/0x4c0 fs/namei.c:4206
       do_rmdir+0x3b5/0x580 fs/namei.c:4265
       __do_sys_unlinkat fs/namei.c:4441 [inline]
       __se_sys_unlinkat fs/namei.c:4435 [inline]
       __x64_sys_unlinkat+0xe0/0xf0 fs/namei.c:4435
       do_syscall_x64 arch/x86/entry/common.c:52 [inline]
       do_syscall_64+0xf5/0x240 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_lock_key[depth] --> &of->mutex --> &ovl_i_mutex_dir_key[depth]

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

3 locks held by syz-executor.2/11429:
 #0: ffff8880225fc420 (sb_writers#35){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:409
 #1: ffff88807a3e1e80 (&ovl_i_mutex_dir_key[depth]/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:830 [inline]
 #1: ffff88807a3e1e80 (&ovl_i_mutex_dir_key[depth]/1){+.+.}-{3:3}, at: do_rmdir+0x263/0x580 fs/namei.c:4253
 #2: ffff88807a3e75b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: inode_lock include/linux/fs.h:795 [inline]
 #2: ffff88807a3e75b0 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}, at: vfs_rmdir+0x101/0x4c0 fs/namei.c:4195

stack backtrace:
CPU: 1 PID: 11429 Comm: syz-executor.2 Not tainted 6.9.0-rc7-syzkaller-00136-gf4345f05c0df #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+0x18cb/0x58e0 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
 ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:654 [inline]
 ovl_nlink_start+0xdc/0x390 fs/overlayfs/util.c:1162
 ovl_do_remove+0x1fa/0xd90 fs/overlayfs/dir.c:893
 vfs_rmdir+0x367/0x4c0 fs/namei.c:4206
 do_rmdir+0x3b5/0x580 fs/namei.c:4265
 __do_sys_unlinkat fs/namei.c:4441 [inline]
 __se_sys_unlinkat fs/namei.c:4435 [inline]
 __x64_sys_unlinkat+0xe0/0xf0 fs/namei.c:4435
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6463a7d547
Code: 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 07 01 00 00 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:00007ffc9d0a4278 EFLAGS: 00000207 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 0000000000000065 RCX: 00007f6463a7d547
RDX: 0000000000000200 RSI: 00007ffc9d0a5420 RDI: 00000000ffffff9c
RBP: 00007f6463ac9336 R08: 00005555564d09db R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000207 R12: 00007ffc9d0a5420
R13: 00007f6463ac9336 R14: 0000000000090f93 R15: 000000000000001e
 </TASK>
BTRFS info (device loop2): last unmount of filesystem c9fe44da-de57-406a-8241-57ec7d4412cf

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/11 03:18 upstream f4345f05c0df f7c35481 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in ovl_nlink_start
2024/04/15 05:35 upstream fe46a7dd189e c8349e48 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs possible deadlock in ovl_nlink_start
* Struck through repros no longer work on HEAD.