crypto: ccm - Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this drops AHASH_REQUEST_ON_STACK by preallocating the ahash request area combined with the skcipher area (which are not used at the same time). [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Ard Biesheuvel <[email protected]> Signed-off-by: Kees Cook <[email protected]> Signed-off-by: Herbert Xu <[email protected]>
penberg · Sep 4, 2018 · ebf533a · ebf533a
1 parent d73d67f
commit ebf533a
Showing 1 changed file with 6 additions and 3 deletions.
diff --git a/crypto/ccm.c b/crypto/ccm.c
@@ -50,7 +50,10 @@ struct crypto_ccm_req_priv_ctx {
 	u32 flags;
 	struct scatterlist src[3];
 	struct scatterlist dst[3];
-	struct skcipher_request skreq;
+	union {
+		struct ahash_request ahreq;
+		struct skcipher_request skreq;
+	};
 };
 
 struct cbcmac_tfm_ctx {
@@ -181,7 +184,7 @@ static int crypto_ccm_auth(struct aead_request *req, struct scatterlist *plain,
 	struct crypto_ccm_req_priv_ctx *pctx = crypto_ccm_reqctx(req);
 	struct crypto_aead *aead = crypto_aead_reqtfm(req);
 	struct crypto_ccm_ctx *ctx = crypto_aead_ctx(aead);
-	AHASH_REQUEST_ON_STACK(ahreq, ctx->mac);
+	struct ahash_request *ahreq = &pctx->ahreq;
 	unsigned int assoclen = req->assoclen;
 	struct scatterlist sg[3];
 	u8 *odata = pctx->odata;
@@ -427,7 +430,7 @@ static int crypto_ccm_init_tfm(struct crypto_aead *tfm)
 	crypto_aead_set_reqsize(
 		tfm,
 		align + sizeof(struct crypto_ccm_req_priv_ctx) +
-		crypto_skcipher_reqsize(ctr));
+		max(crypto_ahash_reqsize(mac), crypto_skcipher_reqsize(ctr)));
 
 	return 0;