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Subject[PATCH v2 06/15] crypto: ahash - fix another early termination in hash walk
Date
From: Eric Biggers <ebiggers@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: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@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
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