linux-kernel - Re: [syzbot] [xfs?] KASAN: slab-use-after-free Read in xfs_buf

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Message-ID: <696dec7b.a70a0220.34546f.043a.GAE@google.com>
Date: Mon, 19 Jan 2026 00:34:03 -0800
From: syzbot <syzbot+0391d34e801643e2809b@...kaller.appspotmail.com>
To: hch@...radead.org, linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [xfs?] KASAN: slab-use-after-free Read in xfs_buf_rele (4)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: MAX_LOCKDEP_KEYS too low!

BUG: MAX_LOCKDEP_KEYS too low!
turning off the locking correctness validator.
CPU: 1 UID: 0 PID: 7123 Comm: syz-executor Not tainted syzkaller #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C)
 __dump_stack+0x30/0x40 lib/dump_stack.c:94
 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 register_lock_class+0x310/0x348 kernel/locking/lockdep.c:1332
 __lock_acquire+0xbc/0x30a4 kernel/locking/lockdep.c:5112
 lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868
 touch_wq_lockdep_map+0xa8/0x164 kernel/workqueue.c:3940
 __flush_workqueue+0xfc/0x109c kernel/workqueue.c:3982
 drain_workqueue+0xa4/0x310 kernel/workqueue.c:4146
 destroy_workqueue+0xb4/0xd90 kernel/workqueue.c:5903
 xfs_destroy_mount_workqueues+0xac/0xdc fs/xfs/xfs_super.c:649
 xfs_fs_put_super+0x128/0x144 fs/xfs/xfs_super.c:1262
 generic_shutdown_super+0x12c/0x2b8 fs/super.c:643
 kill_block_super+0x44/0x90 fs/super.c:1722
 xfs_kill_sb+0x20/0x58 fs/xfs/xfs_super.c:2297
 deactivate_locked_super+0xc4/0x12c fs/super.c:474
 deactivate_super+0xe0/0x100 fs/super.c:507
 cleanup_mnt+0x31c/0x3ac fs/namespace.c:1318
 __cleanup_mnt+0x20/0x30 fs/namespace.c:1325
 task_work_run+0x1dc/0x260 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
 exit_to_user_mode_loop+0x10c/0x18c kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 exit_to_user_mode_prepare_legacy include/linux/irq-entry-common.h:242 [inline]
 arm64_exit_to_user_mode arch/arm64/kernel/entry-common.c:81 [inline]
 el0_svc+0x17c/0x26c arch/arm64/kernel/entry-common.c:725
 el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:743
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb
XFS (loop0): Unmounting Filesystem c496e05e-540d-4c72-b591-04d79d8b4eeb


Tested on:

commit:         3e548540 increase LOCKDEP_CHAINS_BITS
git tree:       git://git.infradead.org/users/hch/xfs.git xfs-buf-hash
console output: https://syzkaller.appspot.com/x/log.txt?x=101b0d22580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6c6138f827b10ea4
dashboard link: https://syzkaller.appspot.com/bug?extid=0391d34e801643e2809b
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
userspace arch: arm64

Note: no patches were applied.