Commit b61907bb authored by Herbert Xu's avatar Herbert Xu

crypto: shash - Fix zero-length shash ahash digest crash

The shash ahash digest adaptor function may crash if given a
zero-length input together with a null SG list.  This is because
it tries to read the SG list before looking at the length.

This patch fixes it by checking the length first.

Cc: <>
Reported-by: Stephan Müller<>
Signed-off-by: default avatarHerbert Xu <>
Tested-by: default avatarStephan Müller <>
parent 0cabf2af
......@@ -275,12 +275,14 @@ static int shash_async_finup(struct ahash_request *req)
int shash_ahash_digest(struct ahash_request *req, struct shash_desc *desc)
struct scatterlist *sg = req->src;
unsigned int offset = sg->offset;
unsigned int nbytes = req->nbytes;
struct scatterlist *sg;
unsigned int offset;
int err;
if (nbytes < min(sg->length, ((unsigned int)(PAGE_SIZE)) - offset)) {
if (nbytes &&
(sg = req->src, offset = sg->offset,
nbytes < min(sg->length, ((unsigned int)(PAGE_SIZE)) - offset))) {
void *data;
data = kmap_atomic(sg_page(sg));
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