CVE-2025-38620

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

zloop: fix KASAN use-after-free of tag set

When a zoned loop device, or zloop device, is removed, KASAN enabled kernel reports BUG KASAN use-after-free in blk_mq_free_tag_set(). The BUG happens because zloop_ctl_remove() calls put_disk(), which invokes zloop_free_disk(). The zloop_free_disk() frees the memory allocated for the zlo pointer. However, after the memory is freed, zloop_ctl_remove() calls blk_mq_free_tag_set(&zlo->tag_set), which accesses the freed zlo. Hence the KASAN use-after-free.

zloop_ctl_remove() put_disk(zlo->disk) put_device() kobject_put() … zloop_free_disk() kvfree(zlo) blk_mq_free_tag_set(&zlo->tag_set)

To avoid the BUG, move the call to blk_mq_free_tag_set(&zlo->tag_set) from zloop_ctl_remove() into zloop_free_disk(). This ensures that the tag_set is freed before the call to kvfree(zlo).

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/765761851d89c772f482494d452e266795460278
• https://git.kernel.org/stable/c/c7c87046b41a9ef28ee7ac476c369da5b5228bc5