CVE-2025-40063

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

crypto: comp - Use same definition of context alloc and free ops

In commit 42d9f6c77479 ("crypto: acomp - Move scomp stream allocation code into acomp"), the crypto_acomp_streams struct was made to rely on having the alloc_ctx and free_ctx operations defined in the same order as the scomp_alg struct. But in that same commit, the alloc_ctx and free_ctx members of scomp_alg may be randomized by structure layout randomization, since they are contained in a pure ops structure (containing only function pointers). If the pointers within scomp_alg are randomized, but those in crypto_acomp_streams are not, then the order may no longer match. This fixes the problem by removing the union from scomp_alg so that both crypto_acomp_streams and scomp_alg will share the same definition of alloc_ctx and free_ctx, ensuring they will always have the same layout.

The crypto compression framework relied on identical layout of alloc_ctx and free_ctx between scomp_alg and crypto_acomp_streams. Structure randomization (CONFIG_RANDSTRUCT) could reorder function pointers in scomp_alg, leading to mismatched allocation/free operations and potential crashes in compression drivers (LZO, LZ4, NX842). Exploitation is highly unlikely: it requires local access and the ability to register or load custom crypto algorithms via the AF_ALG/crypto API.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.