crypto: cryptd - Use request context instead of stack for sub-request

cryptd is buggy as it tries to use sync_skcipher without going
through the proper sync_skcipher interface.  In fact it doesn't
even need sync_skcipher since it's already a proper skcipher and
can easily access the request context instead of using something
off the stack.

Fixes: 36b3875a ("crypto: cryptd - Remove VLA usage of skcipher")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/cryptd.c

@@ -68,11 +68,12 @@ struct aead_instance_ctx {
 
 struct cryptd_skcipher_ctx {
 	refcount_t refcnt;
-	struct crypto_sync_skcipher *child;
+	struct crypto_skcipher *child;
 };
 
 struct cryptd_skcipher_request_ctx {
 	crypto_completion_t complete;
+	struct skcipher_request req;
 };
 
 struct cryptd_hash_ctx {
@@ -227,13 +228,13 @@ static int cryptd_skcipher_setkey(struct crypto_skcipher *parent,
 				  const u8 *key, unsigned int keylen)
 {
 	struct cryptd_skcipher_ctx *ctx = crypto_skcipher_ctx(parent);
-	struct crypto_sync_skcipher *child = ctx->child;
+	struct crypto_skcipher *child = ctx->child;
 
-	crypto_sync_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
-	crypto_sync_skcipher_set_flags(child,
-				       crypto_skcipher_get_flags(parent) &
-					 CRYPTO_TFM_REQ_MASK);
-	return crypto_sync_skcipher_setkey(child, key, keylen);
+	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
+	crypto_skcipher_set_flags(child,
+				  crypto_skcipher_get_flags(parent) &
+				  CRYPTO_TFM_REQ_MASK);
+	return crypto_skcipher_setkey(child, key, keylen);
 }
 
 static void cryptd_skcipher_complete(struct skcipher_request *req, int err)
@@ -258,13 +259,13 @@ static void cryptd_skcipher_encrypt(struct crypto_async_request *base,
 	struct cryptd_skcipher_request_ctx *rctx = skcipher_request_ctx(req);
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct cryptd_skcipher_ctx *ctx = crypto_skcipher_ctx(tfm);
-	struct crypto_sync_skcipher *child = ctx->child;
-	SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, child);
+	struct skcipher_request *subreq = &rctx->req;
+	struct crypto_skcipher *child = ctx->child;
 
 	if (unlikely(err == -EINPROGRESS))
 		goto out;
 
-	skcipher_request_set_sync_tfm(subreq, child);
+	skcipher_request_set_tfm(subreq, child);
 	skcipher_request_set_callback(subreq, CRYPTO_TFM_REQ_MAY_SLEEP,
 				      NULL, NULL);
 	skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,
@@ -286,13 +287,13 @@ static void cryptd_skcipher_decrypt(struct crypto_async_request *base,
 	struct cryptd_skcipher_request_ctx *rctx = skcipher_request_ctx(req);
 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 	struct cryptd_skcipher_ctx *ctx = crypto_skcipher_ctx(tfm);
-	struct crypto_sync_skcipher *child = ctx->child;
-	SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, child);
+	struct skcipher_request *subreq = &rctx->req;
+	struct crypto_skcipher *child = ctx->child;
 
 	if (unlikely(err == -EINPROGRESS))
 		goto out;
 
-	skcipher_request_set_sync_tfm(subreq, child);
+	skcipher_request_set_tfm(subreq, child);
 	skcipher_request_set_callback(subreq, CRYPTO_TFM_REQ_MAY_SLEEP,
 				      NULL, NULL);
 	skcipher_request_set_crypt(subreq, req->src, req->dst, req->cryptlen,
@@ -343,9 +344,10 @@ static int cryptd_skcipher_init_tfm(struct crypto_skcipher *tfm)
 	if (IS_ERR(cipher))
 		return PTR_ERR(cipher);
 
-	ctx->child = (struct crypto_sync_skcipher *)cipher;
+	ctx->child = cipher;
 	crypto_skcipher_set_reqsize(
-		tfm, sizeof(struct cryptd_skcipher_request_ctx));
+		tfm, sizeof(struct cryptd_skcipher_request_ctx) +
+		     crypto_skcipher_reqsize(cipher));
 	return 0;
 }
 
@@ -353,7 +355,7 @@ static void cryptd_skcipher_exit_tfm(struct crypto_skcipher *tfm)
 {
 	struct cryptd_skcipher_ctx *ctx = crypto_skcipher_ctx(tfm);
 
-	crypto_free_sync_skcipher(ctx->child);
+	crypto_free_skcipher(ctx->child);
 }
 
 static void cryptd_skcipher_free(struct skcipher_instance *inst)
@@ -931,7 +933,7 @@ struct crypto_skcipher *cryptd_skcipher_child(struct cryptd_skcipher *tfm)
 {
 	struct cryptd_skcipher_ctx *ctx = crypto_skcipher_ctx(&tfm->base);
 
-	return &ctx->child->base;
+	return ctx->child;
 }
 EXPORT_SYMBOL_GPL(cryptd_skcipher_child);