CVE-2025-38709
loop: Avoid updating block size under exclusive owner
Description
In the Linux kernel, the following vulnerability has been resolved: loop: Avoid updating block size under exclusive owner Syzbot came up with a reproducer where a loop device block size is changed underneath a mounted filesystem. This causes a mismatch between the block device block size and the block size stored in the superblock causing confusion in various places such as fs/buffer.c. The particular issue triggered by syzbot was a warning in __getblk_slow() due to requested buffer size not matching block device block size. Fix the problem by getting exclusive hold of the loop device to change its block size. This fails if somebody (such as filesystem) has already an exclusive ownership of the block device and thus prevents modifying the loop device under some exclusive owner which doesn't expect it.
INFO
Published Date :
Sept. 4, 2025, 4:15 p.m.
Last Modified :
Sept. 5, 2025, 5:47 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Acquire exclusive hold before changing loop device block size.
- Fail if exclusive ownership already exists.
- Update block size only under exclusive ownership.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-38709.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-38709 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-38709
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2025-38709 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2025-38709 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 04, 2025
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: loop: Avoid updating block size under exclusive owner Syzbot came up with a reproducer where a loop device block size is changed underneath a mounted filesystem. This causes a mismatch between the block device block size and the block size stored in the superblock causing confusion in various places such as fs/buffer.c. The particular issue triggered by syzbot was a warning in __getblk_slow() due to requested buffer size not matching block device block size. Fix the problem by getting exclusive hold of the loop device to change its block size. This fails if somebody (such as filesystem) has already an exclusive ownership of the block device and thus prevents modifying the loop device under some exclusive owner which doesn't expect it. Added Reference https://git.kernel.org/stable/c/139a000d20f2f38ce34296feddd641d730fe1c08 Added Reference https://git.kernel.org/stable/c/5d67b30aefeb7a949040bbb1b4e3b84c5d29a624 Added Reference https://git.kernel.org/stable/c/7e49538288e523427beedd26993d446afef1a6fb Added Reference https://git.kernel.org/stable/c/b928438cc87c0bf7ae078e4b7b6e14261e84c5c5 Added Reference https://git.kernel.org/stable/c/ce8da5d13d8c2a7b30b2fb376a22e8eb1a70b8bb