[PATCH v2 06/15] crypto: ahash - fix another early termination in hash walk

[Eric Biggers]

From: Eric Biggers <ebigg...@google.com>

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: sta...@vger.kernel.org
Signed-off-by: Eric Biggers <ebigg...@google.com>
---
 crypto/ahash.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/crypto/ahash.c b/crypto/ahash.c
index ca0d3e281fefb..81e2767e2164e 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);
-- 
2.20.1