Re: [PATCH] fsverity: reject short BPF digest buffers

[Eric Biggers]

On Wed, Aug 05, 2026 at 03:56:55PM +0800, Yichong Chen wrote:
> bpf_get_fsverity_digest() reports the digest size as the full hash digest
> size.  However, when the provided dynptr only has room for part of the
> digest, the helper currently copies the truncated digest and still returns
> success.
> 
> Returning success with a digest_size that is larger than the actual copied
> digest is misleading for integrity policy code.  Match the ioctl
> measurement path and reject too-small output buffers with -EOVERFLOW.
> 
> Fixes: 67814c00de31 ("bpf, fsverity: Add kfunc bpf_get_fsverity_digest")
> Signed-off-by: Yichong Chen <chenyichong@xxxxxxxxxxxxx>
> ---
>  fs/verity/measure.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Already handled by https://lore.kernel.org/bpf/20260803181232.14743-1-ebiggers@xxxxxxxxxx/

- Eric