linux-kernel - Re: [syzbot] [ext4?] possible deadlock in ext4

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Message-ID: <68ac60e7.a70a0220.303e5.0003.GAE@google.com>
Date: Mon, 25 Aug 2025 06:11:03 -0700
From: syzbot <syzbot+c5c9c223a721d7353490@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [ext4?] possible deadlock in ext4_truncate (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING: locking bug in ext4_truncate

------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(subclass >= MAX_LOCKDEP_SUBCLASSES)
WARNING: CPU: 0 PID: 6286 at kernel/locking/lockdep.c:5103 __lock_acquire+0x10ba/0x1ce0 kernel/locking/lockdep.c:5103
Modules linked in:
CPU: 0 UID: 65534 PID: 6286 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:__lock_acquire+0x10ba/0x1ce0 kernel/locking/lockdep.c:5103
Code: 41 83 bd d4 0a 00 00 01 19 f6 83 e6 02 83 c6 03 e9 5b f9 ff ff 90 48 c7 c6 80 a8 c8 8d 48 c7 c7 0c 44 e1 8d e8 b7 7f e2 ff 90 <0f> 0b 90 90 e9 5b f8 ff ff 90 48 c7 c6 f6 98 e2 8d 48 c7 c7 0c 44
RSP: 0018:ffffc90002eb7920 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000008 RCX: ffffffff817a3358
RDX: ffff88807ad25a00 RSI: ffffffff817a3365 RDI: 0000000000000001
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 000000002d2d2d2d R12: 000000009af27c01
R13: ffff88807ad25a00 R14: 0000000000000000 R15: ffff88805d1b6210
FS:  0000555565c94500(0000) GS:ffff8881246bd000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcca85bf18 CR3: 000000005dcbb000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825
 down_write_nested+0x96/0x210 kernel/locking/rwsem.c:1706
 ext4_truncate+0xdec/0x1220 fs/ext4/inode.c:4640
 ext4_evict_inode+0x7a8/0x18e0 fs/ext4/inode.c:261
 evict+0x3e6/0x920 fs/inode.c:810
 iput_final fs/inode.c:1897 [inline]
 iput fs/inode.c:1923 [inline]
 iput+0x521/0x880 fs/inode.c:1909
 d_delete_notify include/linux/fsnotify.h:377 [inline]
 vfs_rmdir fs/namei.c:4474 [inline]
 vfs_rmdir+0x487/0x690 fs/namei.c:4438
 do_rmdir+0x2e8/0x3c0 fs/namei.c:4516
 __do_sys_unlinkat fs/namei.c:4690 [inline]
 __se_sys_unlinkat fs/namei.c:4684 [inline]
 __x64_sys_unlinkat+0xef/0x130 fs/namei.c:4684
 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: 0033:0x7f43c538e1c7
Code: 73 01 c3 48 c7 c1 a8 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffcca85c6c8 EFLAGS: 00000207 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 0000000000000065 RCX: 00007f43c538e1c7
RDX: 0000000000000200 RSI: 00007ffcca85d810 RDI: 00000000ffffff9c
RBP: 00007f43c5411c05 R08: 0000555565ca754b R09: 0000000000000000
R10: 0000000000000100 R11: 0000000000000207 R12: 00007ffcca85d810
R13: 00007f43c5411c05 R14: 0000000000026c6d R15: 00007ffcca85d850
 </TASK>


Tested on:

commit:         1b237f19 Linux 6.17-rc3
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1525ec42580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=da02162f945f3311
dashboard link: https://syzkaller.appspot.com/bug?extid=c5c9c223a721d7353490
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1636fa34580000