From: Eric Biggers Date: Mon, 3 Aug 2026 18:12:32 +0000 (-0700) Subject: fsverity: Fix silent truncation in bpf_get_fsverity_digest() X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=7c68ed5c5ad4c185ea9654f5d8ee36560277b7dd;p=thirdparty%2Fkernel%2Flinux.git fsverity: Fix silent truncation in bpf_get_fsverity_digest() bpf_get_fsverity_digest() silently truncates the digest if the provided buffer is too small. This is a footgun, and it doesn't match the semantics of the equivalent UAPI (FS_IOC_MEASURE_VERITY). Change it to return -EOVERFLOW instead, matching FS_IOC_MEASURE_VERITY. Fixes: 67814c00de31 ("bpf, fsverity: Add kfunc bpf_get_fsverity_digest") Signed-off-by: Eric Biggers Acked-by: Song Liu Cc: stable@vger.kernel.org Link: https://lore.kernel.org/bpf/20260803181232.14743-3-ebiggers@kernel.org Signed-off-by: Kumar Kartikeya Dwivedi --- diff --git a/fs/verity/measure.c b/fs/verity/measure.c index f8b3526af004..68dfccb69772 100644 --- a/fs/verity/measure.c +++ b/fs/verity/measure.c @@ -144,14 +144,15 @@ __bpf_kfunc int bpf_get_fsverity_digest(struct file *file, const struct bpf_dynp hash_alg = vi->tree_params.hash_alg; + out_digest_sz = dynptr_sz - sizeof(struct fsverity_digest); + if (out_digest_sz < hash_alg->digest_size) + return -EOVERFLOW; + arg->digest_algorithm = hash_alg - fsverity_hash_algs; arg->digest_size = hash_alg->digest_size; - out_digest_sz = dynptr_sz - sizeof(struct fsverity_digest); - /* copy digest */ - memcpy(arg->digest, vi->file_digest, - min(hash_alg->digest_size, out_digest_sz)); + memcpy(arg->digest, vi->file_digest, hash_alg->digest_size); /* fill the extra buffer with zeros */ if (out_digest_sz > hash_alg->digest_size)