CVE-2025-39917bpf: Fix out-of-bounds dynptr write in bpf_crypto_crypt

Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix out-of-bounds dynptr write in bpf_crypto_crypt Stanislav reported that in bpf_crypto_crypt() the destination dynptr's size is not validated to be at least as large as the source dynptr's size before calling into the crypto backend with 'len = src_len'. This can result in an OOB write when the destination is smaller than the source. Concretely, in mentioned function, psrc and pdst are both linear buffers fetched from each dynptr: psrc = __bpf_dynptr_data(src, src_len); [...] pdst = __bpf_dynptr_data_rw(dst, dst_len); [...] err = decrypt ? ctx->type->decrypt(ctx->tfm, psrc, pdst, src_len, piv) : ctx->type->encrypt(ctx->tfm, psrc, pdst, src_len, piv); The crypto backend expects pdst to be large enough with a src_len length that can be written. Add an additional src_len > dst_len check and bail out if it's the case. Note that these kfuncs are accessible under root privileges only.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/0126358df12d6f476f79251d9c398ac5c1b3062d
• https://git.kernel.org/stable/c/c4be24ef0510c146dca4671effb127e97631534b
• https://git.kernel.org/stable/c/f9bb6ffa7f5ad0f8ee0f53fc4a10655872ee4a14