CVE-2025-21672

In the Linux kernel, the following vulnerability has been resolved:

afs: Fix merge preference rule failure condition

syzbot reported a lock held when returning to userspace[1]. This is because if argc is less than 0 and the function returns directly, the held inode lock is not released.

Fix this by store the error in ret and jump to done to clean up instead of returning directly.

[dh: Modified Lizhi Xus original patch to make it honour the error code from afs_split_string()]

[1] WARNING: lock held when returning to user space! 6.13.0-rc3-syzkaller-00209-g499551201b5f #0 Not tainted

syz-executor133/5823 is leaving the kernel with locks still held! 1 lock held by syz-executor133/5823: #0: ffff888071cffc00 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: inode_lock include/linux/fs.h:818 [inline] #0: ffff888071cffc00 (&sb->s_type->i_mutex_key#9){++++}-{4:4}, at: afs_proc_addr_prefs_write+0x2bb/0x14e0 fs/afs/addr_prefs.c:388

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/17a4fde81d3a7478d97d15304a6d61094a10c2e3
• https://git.kernel.org/stable/c/22be1d90a6211c88dd093b25d1f3aa974d0d9f9d