UBUNTU-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.
02 / AFFECTED SOFTWARE
Affected packages
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78 explicit affected versions
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03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/f75f66683ded09f7135aef2e763c245a07c8271a
- https://git.kernel.org/stable/c/779d3b6f2d32c5f1da6163e959abe1e1ffe2945b
- https://git.kernel.org/stable/c/f75f66683ded09f7135aef2e763c245a07c8271a
- https://ubuntu.com/security/CVE-2025-40063
- https://ubuntu.com/security/notices/USN-8029-1
- https://ubuntu.com/security/notices/USN-8029-2
- https://ubuntu.com/security/notices/USN-8029-3
- https://ubuntu.com/security/notices/USN-8030-1
- https://ubuntu.com/security/notices/USN-8048-1
- https://www.cve.org/CVERecord?id=CVE-2025-40063