CVE-2025-38620
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-08-22

Last updated on: 2025-11-26

Assigner: kernel.org

Description
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).
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Meta Information
Published
2025-08-22
Last Modified
2025-11-26
Generated
2026-06-16
AI Q&A
2025-08-22
EPSS Evaluated
2026-06-15
NVD
CVE-2025-38620
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel 6.16
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-416 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 Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
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Executive Summary

This vulnerability is a use-after-free bug in the Linux kernel's zoned loop (zloop) device driver. When a zloop device is removed, the kernel frees memory for a structure (zlo) but then later accesses that freed memory, causing a KASAN (Kernel Address Sanitizer) use-after-free error. Specifically, the function zloop_ctl_remove() calls put_disk(), which eventually frees the zlo memory, but then calls blk_mq_free_tag_set() on a tag_set inside the freed memory, leading to the bug. The fix moves the call to blk_mq_free_tag_set() before the memory is freed to prevent accessing freed memory.

Impact Analysis

This vulnerability can cause the Linux kernel to access freed memory, leading to kernel crashes or instability. It may also expose the system to potential security risks such as memory corruption or exploitation by attackers to execute arbitrary code or cause denial of service.

Mitigation Strategies

To mitigate this vulnerability, ensure that your Linux kernel is updated to a version where the zloop device fix is applied. The fix involves moving the call to blk_mq_free_tag_set() into zloop_free_disk() to prevent use-after-free errors. Applying the latest kernel patches or updates that include this fix will prevent the KASAN use-after-free BUG.

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