crypto: skcipher - Fix blkcipher walk OOM crash

[ Upstream commit acdb04d0b36769b3e05990c488dc74d8b7ac8060 ]

When we need to allocate a temporary blkcipher_walk_next and it
fails, the code is supposed to take the slow path of processing
the data block by block.  However, due to an unrelated change
we instead end up dereferencing the NULL pointer.

This patch fixes it by moving the unrelated bsize setting out
of the way so that we enter the slow path as inteded.

Fixes: 7607bd8ff03b ("[CRYPTO] blkcipher: Added blkcipher_walk_virt_block")
Cc: stable@vger.kernel.org
Reported-by: xiakaixu <xiakaixu@huawei.com>
Reported-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

diff --git a/crypto/blkcipher.c b/crypto/blkcipher.c
index 0122bec38564d6c5de533d0e80b03d23e95f673b..f25799f351f722b8ea48280458ebe18161b617e8 100644 (file)
--- a/crypto/blkcipher.c
+++ b/crypto/blkcipher.c
@@ -233,6 +233,8 @@ static int blkcipher_walk_next(struct blkcipher_desc *desc,
                return blkcipher_walk_done(desc, walk, -EINVAL);
        }
 
+       bsize = min(walk->walk_blocksize, n);
+
        walk->flags &= ~(BLKCIPHER_WALK_SLOW | BLKCIPHER_WALK_COPY |
                         BLKCIPHER_WALK_DIFF);
        if (!scatterwalk_aligned(&walk->in, walk->alignmask) ||
@@ -245,7 +247,6 @@ static int blkcipher_walk_next(struct blkcipher_desc *desc,
                }
        }
 
-       bsize = min(walk->walk_blocksize, n);
        n = scatterwalk_clamp(&walk->in, n);
        n = scatterwalk_clamp(&walk->out, n);