[syzbot] [ext4?] WARNING: bad unlock balance in ext4_rename2

[syzbot] [ext4?] WARNING: bad unlock balance in ext4_rename2

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    0988a0ea7919 Merge tag 'for-v6.3-part2' of git://git.kerne..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146f3638c80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f763d89e26d3d4c4
dashboard link: https://syzkaller.appspot.com/bug?extid=0c73d1d8b952c5f3d714
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e0aa29e9ae74/disk-0988a0ea.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6f64db0b58ef/vmlinux-0988a0ea.xz
kernel image: https://storage.googleapis.com/syzbot-assets/db391408e15d/bzImage-0988a0ea.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0c73d1d8b952c5f3d714@syzkaller.appspotmail.com

EXT4-fs (loop3): warning: checktime reached, running e2fsck is recommended
EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 without journal. Quota mode: none.
=====================================
WARNING: bad unlock balance detected!
6.2.0-syzkaller-13467-g0988a0ea7919 #0 Not tainted
-------------------------------------
syz-executor.3/8027 is trying to release lock (&type->i_mutex_dir_key) at:
[<ffffffff82448753>] inode_unlock include/linux/fs.h:763 [inline]
[<ffffffff82448753>] ext4_rename fs/ext4/namei.c:4017 [inline]
[<ffffffff82448753>] ext4_rename2+0x3d03/0x4410 fs/ext4/namei.c:4193
but there are no more locks to release!

other info that might help us debug this:
2 locks held by syz-executor.3/8027:
 #0: ffff888026e42460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394
 #1: ffff888034ec0e08 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: lock_rename+0x186/0x1a0

stack backtrace:
CPU: 0 PID: 8027 Comm: syz-executor.3 Not tainted 6.2.0-syzkaller-13467-g0988a0ea7919 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106
 print_unlock_imbalance_bug+0x252/0x2c0 kernel/locking/lockdep.c:5109
 __lock_release kernel/locking/lockdep.c:5346 [inline]
 lock_release+0x63c/0xab0 kernel/locking/lockdep.c:5689
 up_write+0x79/0x580 kernel/locking/rwsem.c:1625
 inode_unlock include/linux/fs.h:763 [inline]
 ext4_rename fs/ext4/namei.c:4017 [inline]
 ext4_rename2+0x3d03/0x4410 fs/ext4/namei.c:4193
 vfs_rename+0xb1b/0xfa0 fs/namei.c:4772
 do_renameat2+0xb9b/0x13c0 fs/namei.c:4923
 __do_sys_rename fs/namei.c:4969 [inline]
 __se_sys_rename fs/namei.c:4967 [inline]
 __x64_sys_rename+0x86/0x90 fs/namei.c:4967
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f6ffe68c0f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6fff35c168 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007f6ffe7abf80 RCX: 00007f6ffe68c0f9
RDX: 0000000000000000 RSI: 0000000020000180 RDI: 00000000200000c0
RBP: 00007f6ffe6e7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd65e8771f R14: 00007f6fff35c300 R15: 0000000000022000
 </TASK>
------------[ cut here ]------------
DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && !rwsem_test_oflags(sem, RWSEM_NONSPINNABLE)): count = 0x0, magic = 0xffff888034c0abb0, owner = 0x0, curr 0xffff88802bd9ba80, list empty
WARNING: CPU: 0 PID: 8027 at kernel/locking/rwsem.c:1370 __up_write kernel/locking/rwsem.c:1369 [inline]
WARNING: CPU: 0 PID: 8027 at kernel/locking/rwsem.c:1370 up_write+0x4f4/0x580 kernel/locking/rwsem.c:1626
Modules linked in:
CPU: 0 PID: 8027 Comm: syz-executor.3 Not tainted 6.2.0-syzkaller-13467-g0988a0ea7919 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
RIP: 0010:__up_write kernel/locking/rwsem.c:1369 [inline]
RIP: 0010:up_write+0x4f4/0x580 kernel/locking/rwsem.c:1626
Code: 48 c7 c7 a0 7e 0a 8b 48 c7 c6 40 81 0a 8b 48 8b 54 24 28 48 8b 4c 24 18 4d 89 e0 4c 8b 4c 24 30 53 e8 60 58 e8 ff 48 83 c4 08 <0f> 0b e9 75 fd ff ff 48 c7 c1 68 a0 74 8e 80 e1 07 80 c1 03 38 c1
RSP: 0018:ffffc90015fc7680 EFLAGS: 00010292
RAX: 0c10b1842f27c000 RBX: ffffffff8b0a7f80 RCX: 0000000000040000
RDX: ffffc9000c513000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: ffffc90015fc7750 R08: ffffffff8153a8b2 R09: fffff52002bf8e49
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000000
R13: ffff888034c0abb0 R14: 1ffff92002bf8ed8 R15: dffffc0000000000
FS:  00007f6fff35c700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000056388d3a46b0 CR3: 000000002bc04000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 inode_unlock include/linux/fs.h:763 [inline]
 ext4_rename fs/ext4/namei.c:4017 [inline]
 ext4_rename2+0x3d03/0x4410 fs/ext4/namei.c:4193
 vfs_rename+0xb1b/0xfa0 fs/namei.c:4772
 do_renameat2+0xb9b/0x13c0 fs/namei.c:4923
 __do_sys_rename fs/namei.c:4969 [inline]
 __se_sys_rename fs/namei.c:4967 [inline]
 __x64_sys_rename+0x86/0x90 fs/namei.c:4967
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f6ffe68c0f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6fff35c168 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007f6ffe7abf80 RCX: 00007f6ffe68c0f9
RDX: 0000000000000000 RSI: 0000000020000180 RDI: 00000000200000c0
RBP: 00007f6ffe6e7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd65e8771f R14: 00007f6fff35c300 R15: 0000000000022000
 </TASK>


---
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Re: [syzbot] [ext4?] WARNING: bad unlock balance in ext4_rename2

[Eric Biggers]

On Mon, Mar 06, 2023 at 03:34:40AM -0800, syzbot wrote:
> =====================================
> WARNING: bad unlock balance detected!
> 6.2.0-syzkaller-13467-g0988a0ea7919 #0 Not tainted
> -------------------------------------
> syz-executor.3/8027 is trying to release lock (&type->i_mutex_dir_key) at:
> [<ffffffff82448753>] inode_unlock include/linux/fs.h:763 [inline]
> [<ffffffff82448753>] ext4_rename fs/ext4/namei.c:4017 [inline]
> [<ffffffff82448753>] ext4_rename2+0x3d03/0x4410 fs/ext4/namei.c:4193
> but there are no more locks to release!

I think this is the same as
"[bug report] ext4: Fix possible corruption when moving a directory"
(https://lore.kernel.org/linux-ext4/5efbe1b9-ad8b-4a4f-b422-24824d2b775c@kili.mountain).
See there for the root cause (double unlock).

- Eric

Re: [syzbot] [ext4?] WARNING: bad unlock balance in ext4_rename2

[Theodore Ts'o]

#syz fix: ext4: fix possible double unlock when moving a directory