Linux Kernel 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 Linux kernel crypto compression subsystem is affected on builds that include commit 42d9f6c77479 ("crypto: acomp - Move scomp stream allocation code into acomp") and enable structure layout randomization (CONFIG_RANDSTRUCT). No CPE list or precise version range was provided in the intelligence set; the affected and fixed revisions are identified only by the two kernel.org stable git commits (779d3b6f2d32c5f1da6163e959abe1e1ffe2945b and f75f66683ded09f7135aef2e763c245a07c8271a). Exact tagged stable release numbers should be confirmed against the kernel.org stable trees referenced at https://git.kernel.org/stable/c/779d3b6f2d32c5f1da6163e959abe1e1ffe2945b and https://git.kernel.org/stable/c/f75f66683ded09f7135aef2e763c245a07c8271a.