dm: dm-crypt: Do not partially accept write BIOs with zoned targets

Summary

CVE	CVE-2025-39791
State	PUBLISHED
Assigner	Linux
Source Priority	CVE Program / NVD first with legacy fallback
Published	2025-09-11 17:15:45 UTC
Updated	2026-07-30 06:23:45 UTC
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.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem Types: CWE-667

Version	Source	Type	Score	Severity	Vector
3.1	[email protected]	Primary	5.5	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`
3.1	416baaa9-dc9f-4396-8d5f-8c081fb06d67	Secondary	7.8	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`
3.1	CNA	DECLARED	7.8	HIGH	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`

CVSS v3.1 Breakdown

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

Type	Vendor	Product	Version	Update	Edition	Language
Operating System	Linux	Linux Kernel	All	All	All	All

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Linux	Linux	affected f211268ed1f9bdf48f06a3ead5f5d88437450579 8864616719b6bbf92356bc89ff544b0cd484c656 git	Not specified
CNA	Linux	Linux	affected f211268ed1f9bdf48f06a3ead5f5d88437450579 52a2c4c60470352acf9cde7a2dfa661c1e67e796 git	Not specified
CNA	Linux	Linux	affected f211268ed1f9bdf48f06a3ead5f5d88437450579 e549663849e5bb3b985dc2d293069f0d9747ae72 git	Not specified
CNA	Linux	Linux	affected 6.10	Not specified
CNA	Linux	Linux	unaffected 6.10 semver	Not specified
CNA	Linux	Linux	unaffected 6.12.44 6.12.* semver	Not specified
CNA	Linux	Linux	unaffected 6.16.4 6.16.* semver	Not specified
CNA	Linux	Linux	unaffected 6.17 * original_commit_for_fix	Not specified

References

Reference	Source	Link	Tags
git.kernel.org/stable/c/52a2c4c60470352acf9cde7a2dfa661c1e67e796	416baaa9-dc9f-4396-8d5f-8c081fb06d67	git.kernel.org	Patch
git.kernel.org/stable/c/8864616719b6bbf92356bc89ff544b0cd484c656	416baaa9-dc9f-4396-8d5f-8c081fb06d67	git.kernel.org	Patch
git.kernel.org/stable/c/e549663849e5bb3b985dc2d293069f0d9747ae72	416baaa9-dc9f-4396-8d5f-8c081fb06d67	git.kernel.org	Patch
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

There are currently no legacy QID mappings associated with this CVE.