CVE-2026-74590fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions

Official description

In the Linux kernel, the following vulnerability has been resolved: fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions The BPF verifier and the dynptr abstraction ensure that the memory space referenced by a dynptr remains valid. They do not, however, provide any guarantee that the contents of the memory are stable. kfuncs are expected to remain memory-safe even if concurrent modifications occur. bpf_get_fsverity_digest() didn't follow that: it could crash if arg->digest_size was concurrently modified. Fix that by using the known-good value hash_alg->digest_size instead. Also widen 'dynptr_sz' and 'out_digest_sz' to u64 to match the return type of __bpf_dynptr_size(). It doesn't appear that it can actually be more than INT_MAX currently (since __bpf_dynptr_data_rw() excludes file-based pointers), but the correct type might as well be used.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/1344b632cb5043e32939a84568125719111c5af3
• https://git.kernel.org/stable/c/2a5cfcad1d56e26d645b7887b0ed24c371851525
• https://git.kernel.org/stable/c/5bd63cad9df4328a184c409fbdad4f17944bcdb8
• https://git.kernel.org/stable/c/3e8ec7c0387273329374f5c7bd61f5f38af71fe1