CVE-2026-89574dm array: validate array block headers on read

Official description

In the Linux kernel, the following vulnerability has been resolved: dm array: validate array block headers on read array_block_check() validates blocknr and csum and nothing else, while node_check(), next to it, has bounded the structural fields since both were written. dm_array_cursor_next() takes its loop bound from the on-disk nr_entries and element_at() is unguarded pointer arithmetic, so a count larger than the block holds keeps the cursor in one block while the index grows past it and the read walks off the dm-bufio buffer -- dm_cache_load_mappings() drives it once per cache block at activation. Check the header against itself: reject a zero value_size, require max_entries to equal calc_max_entries() for that value_size and block size, and require nr_entries to fit. Equality rather than an upper bound, since a count below the real capacity trips BUG_ON() in fill_ablock() and trim_ablock(). Metadata dm-array writes satisfies all three.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e09d8b34ed199c8b7d7528c2b8324aa7cff712f8
• https://git.kernel.org/stable/c/0e3b8f371c385c212b6e6f76c66f5b3f5bcfea62
• https://git.kernel.org/stable/c/67adda7ed5da3e3b64f5b9021a02c21fb374fd9c
• https://git.kernel.org/stable/c/b33f76d33aaeacf3baf3370d8d64985169b36600
• https://git.kernel.org/stable/c/9808ddffb4bc659352df3020cd84d9d864820ee5
• https://git.kernel.org/stable/c/2965787723084835b18dfe993cd450ebf5bd4540