crypto: essiv - Check ssize for decryption and in-place encryption

Move the ssize check to the start in essiv_aead_crypt so that
it's also checked for decryption and in-place encryption.

Reported-by: Muhammad Alifa Ramdhan <ramdhan@starlabs.sg>
Fixes: be1eb7f ("crypto: essiv - create wrapper template for ESSIV generation")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: herbertx

crypto/essiv.c

@@ -186,9 +186,14 @@ static int essiv_aead_crypt(struct aead_request *req, bool enc)
 	const struct essiv_tfm_ctx *tctx = crypto_aead_ctx(tfm);
 	struct essiv_aead_request_ctx *rctx = aead_request_ctx(req);
 	struct aead_request *subreq = &rctx->aead_req;
+	int ivsize = crypto_aead_ivsize(tfm);
+	int ssize = req->assoclen - ivsize;
 	struct scatterlist *src = req->src;
 	int err;
 
+	if (ssize < 0)
+		return -EINVAL;
+
 	crypto_cipher_encrypt_one(tctx->essiv_cipher, req->iv, req->iv);
 
 	/*
@@ -198,19 +203,12 @@ static int essiv_aead_crypt(struct aead_request *req, bool enc)
 	 */
 	rctx->assoc = NULL;
 	if (req->src == req->dst || !enc) {
-		scatterwalk_map_and_copy(req->iv, req->dst,
-					 req->assoclen - crypto_aead_ivsize(tfm),
-					 crypto_aead_ivsize(tfm), 1);
+		scatterwalk_map_and_copy(req->iv, req->dst, ssize, ivsize, 1);
 	} else {
 		u8 *iv = (u8 *)aead_request_ctx(req) + tctx->ivoffset;
-		int ivsize = crypto_aead_ivsize(tfm);
-		int ssize = req->assoclen - ivsize;
 		struct scatterlist *sg;
 		int nents;
 
-		if (ssize < 0)
-			return -EINVAL;
-
 		nents = sg_nents_for_len(req->src, ssize);
 		if (nents < 0)
 			return -EINVAL;