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crypto: xts,lrw - fix out-of-bounds write after kmalloc failure 

In the generic XTS and LRW algorithms, for input data > 128 bytes, a
temporary buffer is allocated to hold the values to be XOR'ed with the
data before and after encryption or decryption.  If the allocation
fails, the fixed-size buffer embedded in the request buffer is meant to
be used as a fallback --- resulting in more calls to the ECB algorithm,
but still producing the correct result.  However, we weren't correctly
limiting subreq->cryptlen in this case, resulting in pre_crypt()
overrunning the embedded buffer.  Fix this by setting subreq->cryptlen
correctly.

Fixes: f1c131b454 ("crypto: xts - Convert to skcipher")
Fixes: 700cb3f5fe ("crypto: lrw - Convert to skcipher")
Cc: stable@vger.kernel.org # v4.10+
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2017-03-23 13:39:46 -07:00 committed by Herbert Xu
parent efc989fce8
commit 9df0eb180c
2 changed files with 10 additions and 4 deletions
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7
crypto/lrw.c
View File

@ -286,8 +286,11 @@ static int init_crypt(struct skcipher_request *req, crypto_completion_t done)
subreq->cryptlen = LRW_BUFFER_SIZE;
if (req->cryptlen > LRW_BUFFER_SIZE) {
subreq->cryptlen = min(req->cryptlen, (unsigned)PAGE_SIZE);
rctx->ext = kmalloc(subreq->cryptlen, gfp);
unsigned int n = min(req->cryptlen, (unsigned int)PAGE_SIZE);
rctx->ext = kmalloc(n, gfp);
if (rctx->ext)
subreq->cryptlen = n;
}
rctx->src = req->src;

7
crypto/xts.c
View File

@ -230,8 +230,11 @@ static int init_crypt(struct skcipher_request *req, crypto_completion_t done)
subreq->cryptlen = XTS_BUFFER_SIZE;
if (req->cryptlen > XTS_BUFFER_SIZE) {
subreq->cryptlen = min(req->cryptlen, (unsigned)PAGE_SIZE);
rctx->ext = kmalloc(subreq->cryptlen, gfp);
unsigned int n = min(req->cryptlen, (unsigned int)PAGE_SIZE);
rctx->ext = kmalloc(n, gfp);
if (rctx->ext)
subreq->cryptlen = n;
}
rctx->src = req->src;