crypto: ahash - fix another early termination in hash walk

Hash algorithms with an alignmask set, e.g. "xcbc(aes-aesni)" and
"michael_mic", fail the improved hash tests because they sometimes
produce the wrong digest.  The bug is that in the case where a
scatterlist element crosses pages, not all the data is actually hashed
because the scatterlist walk terminates too early.  This happens because
the 'nbytes' variable in crypto_hash_walk_done() is assigned the number
of bytes remaining in the page, then later interpreted as the number of
bytes remaining in the scatterlist element.  Fix it.

Fixes: 900a081f6912 ("crypto: ahash - Fix early termination in hash walk")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 7 insertions, 7 deletions

diff --git a/crypto/ahash.c b/crypto/ahash.c
index ca0d3e281fef..81e2767e2164 100644
--- a/crypto/ahash.c
+++ b/crypto/ahash.c
@@ -86,17 +86,17 @@ static int hash_walk_new_entry(struct crypto_hash_walk *walk)
 int crypto_hash_walk_done(struct crypto_hash_walk *walk, int err)
 {
         unsigned int alignmask = walk->alignmask;
-        unsigned int nbytes = walk->entrylen;
 
         walk->data -= walk->offset;
 
-        if (nbytes && walk->offset & alignmask && !err) {
-                walk->offset = ALIGN(walk->offset, alignmask + 1);
-                nbytes = min(nbytes,
-                             ((unsigned int)(PAGE_SIZE)) - walk->offset);
-                walk->entrylen -= nbytes;
+        if (walk->entrylen && (walk->offset & alignmask) && !err) {
+                unsigned int nbytes;
 
+                walk->offset = ALIGN(walk->offset, alignmask + 1);
+                nbytes = min(walk->entrylen,
+                             (unsigned int)(PAGE_SIZE - walk->offset));
                 if (nbytes) {
+                        walk->entrylen -= nbytes;
                         walk->data += walk->offset;
                         return nbytes;
                 }
@@ -116,7 +116,7 @@ int crypto_hash_walk_done(struct crypto_hash_walk *walk, int err)
         if (err)
                 return err;
 
-        if (nbytes) {
+        if (walk->entrylen) {
                 walk->offset = 0;
                 walk->pg++;
                 return hash_walk_next(walk);