dm-pcache: only hand out initialized cache segments

Overview

In the Linux kernel, the following vulnerability has been resolved:

dm-pcache: only hand out initialized cache segments

get_cache_segment() scans the segment map up to cache->n_segs, the physical device segment count, but cache_segs_init() only initializes the first cache_info->n_segs segments. A crafted image with cache_info->n_segs smaller than the device count leaves the remaining pcache_cache_segment structs zeroed (segment.data == NULL), and the allocator can hand one to cache_kset_close(), which writes through the returned segment's data pointer with no NULL check.

Bound the allocator's search to cache_info->n_segs so only initialized segments are ever returned. A conforming cache sets n_segs equal to the device segment count, so this rejects nothing legitimate.

Affected

• Linux >= 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 < 83e3116283ed2c6a6a1fa662862a4b4d7d2701a2
• Linux >= 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 < 692037ae1a7cfacc2f0c22c6e034c1dfee0e553f
• Linux >= 1d57628ff95b32d5cfa8d8f50e07690c161e9cf0 < 2df0fc042e299bae3c0f60ea5cd2af9285658e9f
• Linux 6.18

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Vendor advisories

• Red Hat VEX · Moderate · updated 2026-09-14 · vex