dm-pcache: validate geometry fields from on-disk cache_info

In the Linux kernel, the following vulnerability has been resolved: dm-pcache: validate geometry fields from on-disk cache_info cache_segs_init() iterates cache_info->n_segs times indexing cache->segments[], which is sized to the cache device geometry, and get_seg_id() takes each segment id from the on-media cache_info and the per-segment next_seg link. Both come from cache device metadata that is only CRC-protected with a fixed public seed, so whoever supplies the cache device on a table load (CAP_SYS_ADMIN) controls them: an oversized n_segs or an out-of-range id drives an out-of-bounds access of cache->segments[] and a wild CACHE_DEV_SEGMENT() pointer into the device mapping -- an out-of-bounds read and write from on-disk data. Reject an n_segs that exceeds the device segment count and a segment id that is out of range before either is used. Valid metadata is unaffected.

Source published

11 Sep 2026 19:42:28 UTC

Source modified

19 Oct 2026 08:45:46 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 3.1 · 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H