CVE-2025-39791
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-11

Last updated on: 2025-11-25

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: dm: dm-crypt: Do not partially accept write BIOs with zoned targets Read and write operations issued to a dm-crypt target may be split according to the dm-crypt internal limits defined by the max_read_size and max_write_size module parameters (default is 128 KB). The intent is to improve processing time of large BIOs by splitting them into smaller operations that can be parallelized on different CPUs. For zoned dm-crypt targets, this BIO splitting is still done but without the parallel execution to ensure that the issuing order of write operations to the underlying devices remains sequential. However, the splitting itself causes other problems: 1) Since dm-crypt relies on the block layer zone write plugging to handle zone append emulation using regular write operations, the reminder of a split write BIO will always be plugged into the target zone write plugged. Once the on-going write BIO finishes, this reminder BIO is unplugged and issued from the zone write plug work. If this reminder BIO itself needs to be split, the reminder will be re-issued and plugged again, but that causes a call to a blk_queue_enter(), which may block if a queue freeze operation was initiated. This results in a deadlock as DM submission still holds BIOs that the queue freeze side is waiting for. 2) dm-crypt relies on the emulation done by the block layer using regular write operations for processing zone append operations. This still requires to properly return the written sector as the BIO sector of the original BIO. However, this can be done correctly only and only if there is a single clone BIO used for processing the original zone append operation issued by the user. If the size of a zone append operation is larger than dm-crypt max_write_size, then the orginal BIO will be split and processed as a chain of regular write operations. Such chaining result in an incorrect written sector being returned to the zone append issuer using the original BIO sector. This in turn results in file system data corruptions using xfs or btrfs. Fix this by modifying get_max_request_size() to always return the size of the BIO to avoid it being split with dm_accpet_partial_bio() in crypt_map(). get_max_request_size() is renamed to get_max_request_sectors() to clarify the unit of the value returned and its interface is changed to take a struct dm_target pointer and a pointer to the struct bio being processed. In addition to this change, to ensure that crypt_alloc_buffer() works correctly, set the dm-crypt device max_hw_sectors limit to be at most BIO_MAX_VECS << PAGE_SECTORS_SHIFT (1 MB with a 4KB page architecture). This forces DM core to split write BIOs before passing them to crypt_map(), and thus guaranteeing that dm-crypt can always accept an entire write BIO without needing to split it. This change does not have any effect on the read path of dm-crypt. Read operations can still be split and the BIO fragments processed in parallel. There is also no impact on the performance of the write path given that all zone write BIOs were already processed inline instead of in parallel. This change also does not affect in any way regular dm-crypt block devices.
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Meta Information
Published
2025-09-11
Last Modified
2025-11-25
Generated
2026-05-07
AI Q&A
2025-09-11
EPSS Evaluated
2026-05-05
NVD
CVE-2025-39791
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
linux linux_kernel From 5.15.160 (inc) to 5.16 (inc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-667 The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
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AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability involves the dm-crypt module in the Linux kernel where write BIOs (block I/O operations) to zoned dm-crypt targets are partially accepted and split incorrectly. The splitting of write BIOs without proper handling causes deadlocks due to queue freezes and can lead to incorrect sector returns during zone append operations. This results in potential file system data corruption, especially affecting file systems like xfs or btrfs. The issue arises because dm-crypt relies on splitting large BIOs for performance, but for zoned targets, this splitting breaks the sequential write order and causes problems in zone append emulation.


How can this vulnerability impact me? :

This vulnerability can cause deadlocks in the Linux kernel's block I/O processing when using dm-crypt with zoned block devices, potentially freezing write operations. Additionally, it can lead to file system data corruption on affected file systems such as xfs or btrfs due to incorrect sector information being returned during zone append operations. This can result in data loss or corruption on encrypted storage devices using dm-crypt with zoned targets.


What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability, update the Linux kernel to a version that includes the fix for CVE-2025-39791. The fix involves changes to dm-crypt to prevent partial acceptance of write BIOs with zoned targets, avoiding deadlocks and data corruption. There are no specific configuration changes or workarounds mentioned, so applying the patched kernel is the recommended immediate step.


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