CVE-2025-38709
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-04

Last updated on: 2025-12-03

Assigner: kernel.org

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.
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Meta Information
Published
2025-09-04
Last Modified
2025-12-03
Generated
2026-05-07
AI Q&A
2025-09-04
EPSS Evaluated
2026-05-05
NVD
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
linux linux_kernel to 6.6.109 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.43 (exc)
linux linux_kernel From 6.13 (inc) to 6.15.11 (exc)
linux linux_kernel From 6.16 (inc) to 6.16.2 (exc)
Helpful Resources
Exploitability
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CWE ID Description
CWE-NVD-CWE-noinfo
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the Linux kernel's loop device where the block size of the device can be changed while a filesystem is mounted on it. This causes a mismatch between the block device's block size and the block size stored in the filesystem's superblock, leading to confusion and errors in the kernel's buffer management. The issue was triggered by a tool called syzbot and caused warnings due to buffer size mismatches. The fix involves ensuring exclusive ownership of the loop device before changing its block size, preventing changes when the device is already exclusively owned by something like a filesystem.


How can this vulnerability impact me? :

This vulnerability can cause kernel warnings and potential instability or data corruption because the filesystem and block device have mismatched block sizes. This mismatch can lead to confusion in buffer management within the kernel, potentially affecting filesystem reliability and data integrity when using loop devices.


What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability, ensure that the Linux kernel is updated to a version where the fix is applied. The fix involves preventing changes to the loop device block size when it is exclusively owned, so applying the patch or kernel update that includes this fix will prevent the issue.


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