CVE-2025-39917

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.

The patch prevents an out-of-bounds write in bpf_crypto_crypt() by rejecting cases where the source dynptr is larger than the destination (src_len > dst_len). Impact is kernel memory corruption (high integrity/availability impact). For the CVSS the PR:H because these BPF crypto kfuncs are root-only, so only privileged users can invoke them and supply mismatched dynptr sizes.

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.