[PATCH 4.19 017/280] crypto: ccree - dont copy zero size ciphertext

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx>

commit 2b5ac17463dcb2411fed506edcf259a89bb538ba upstream.

For decryption in CBC mode we need to save the last ciphertext block
for use as the next IV. However, we were trying to do this also with
zero sized ciphertext resulting in a panic.

Fix this by only doing the copy if the ciphertext length is at least
of IV size.

Signed-off-by: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/crypto/ccree/cc_cipher.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/crypto/ccree/cc_cipher.c
+++ b/drivers/crypto/ccree/cc_cipher.c
@@ -783,7 +783,8 @@ static int cc_cipher_decrypt(struct skci
 
 	memset(req_ctx, 0, sizeof(*req_ctx));
 
-	if (ctx_p->cipher_mode == DRV_CIPHER_CBC) {
+	if ((ctx_p->cipher_mode == DRV_CIPHER_CBC) &&
+	    (req->cryptlen >= ivsize)) {
 
 		/* Allocate and save the last IV sized bytes of the source,
 		 * which will be lost in case of in-place decryption.