staging: ccree: NULLify backup_info when unused

backup_info field is only allocated for decrypt code path.
The field was not nullified when not used causing a kfree
in an error handling path to attempt to free random
addresses as uncovered in stress testing.

Fixes: 737aed94 ("staging: ccree: save ciphertext for CTS IV")
Cc: stable@vger.kernel.org
Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ccree/ssi_cipher.c

@@ -907,6 +907,7 @@ static int ssi_ablkcipher_encrypt(struct ablkcipher_request *req)
 	unsigned int ivsize = crypto_ablkcipher_ivsize(ablk_tfm);
 
 	req_ctx->is_giv = false;
+	req_ctx->backup_info = NULL;
 
 	return ssi_blkcipher_process(tfm, req_ctx, req->dst, req->src,
 				     req->nbytes, req->info, ivsize,