crypto: ccree - zero all of request ctx before use

In certain error path req_ctx->iv was being freed despite
not being allocated because it was not initialized to NULL.
Rather than play whack a mole with the structure various
field, zero it before use.

This fixes a kernel panic that may occur if an invalid
buffer size was requested triggering the bug above.

Fixes: 63ee04c8b491 ("crypto: ccree - add skcipher support")
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/ccree/cc_cipher.c

@@ -767,7 +767,7 @@ static int cc_cipher_encrypt(struct skcipher_request *req)
 {
 	struct cipher_req_ctx *req_ctx = skcipher_request_ctx(req);
 
-	req_ctx->backup_info = NULL;
+	memset(req_ctx, 0, sizeof(*req_ctx));
 
 	return cc_cipher_process(req, DRV_CRYPTO_DIRECTION_ENCRYPT);
 }
@@ -782,6 +782,8 @@ static int cc_cipher_decrypt(struct skcipher_request *req)
 	gfp_t flags = cc_gfp_flags(&req->base);
 	unsigned int len;
 
+	memset(req_ctx, 0, sizeof(*req_ctx));
+
 	if (ctx_p->cipher_mode == DRV_CIPHER_CBC) {
 
 		/* Allocate and save the last IV sized bytes of the source,
@@ -794,8 +796,6 @@ static int cc_cipher_decrypt(struct skcipher_request *req)
 		len = req->cryptlen - ivsize;
 		scatterwalk_map_and_copy(req_ctx->backup_info, req->src, len,
 					 ivsize, 0);
-	} else {
-		req_ctx->backup_info = NULL;
 	}
 
 	return cc_cipher_process(req, DRV_CRYPTO_DIRECTION_DECRYPT);