crypto: chelsio - permit asynchronous skcipher as fallback

Even though the chelsio driver implements asynchronous versions of
cbc(aes) and xts(aes), the fallbacks it allocates are required to be
synchronous. Given that SIMD based software implementations are usually
asynchronous as well, even though they rarely complete asynchronously
(this typically only happens in cases where the request was made from
softirq context, while SIMD was already in use in the task context that
it interrupted), these implementations are disregarded, and either the
generic C version or another table based version implemented in assembler
is selected instead.

Since falling back to synchronous AES is not only a performance issue, but
potentially a security issue as well (due to the fact that table based AES
is not time invariant), let's fix this, by allocating an ordinary skcipher
as the fallback, and invoke it with the completion routine that was given
to the outer request.

Signed-off-by: Ard Biesheuvel <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/crypto/chelsio/chcr_algo.c

···
 	return min(srclen, dstlen);
 }
 
-static int chcr_cipher_fallback(struct crypto_sync_skcipher *cipher,
-				u32 flags,
-				struct scatterlist *src,
-				struct scatterlist *dst,
-				unsigned int nbytes,
+static int chcr_cipher_fallback(struct crypto_skcipher *cipher,
+				struct skcipher_request *req,
 				u8 *iv,
 				unsigned short op_type)
 {
+	struct chcr_skcipher_req_ctx *reqctx = skcipher_request_ctx(req);
 	int err;
 
-	SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, cipher);
+	skcipher_request_set_tfm(&reqctx->fallback_req, cipher);
+	skcipher_request_set_callback(&reqctx->fallback_req, req->base.flags,
+				      req->base.complete, req->base.data);
+	skcipher_request_set_crypt(&reqctx->fallback_req, req->src, req->dst,
+				   req->cryptlen, iv);
 
-	skcipher_request_set_sync_tfm(subreq, cipher);
-	skcipher_request_set_callback(subreq, flags, NULL, NULL);
-	skcipher_request_set_crypt(subreq, src, dst,
-				   nbytes, iv);
-
-	err = op_type ? crypto_skcipher_decrypt(subreq) :
-		crypto_skcipher_encrypt(subreq);
-	skcipher_request_zero(subreq);
+	err = op_type ? crypto_skcipher_decrypt(&reqctx->fallback_req) :
+			crypto_skcipher_encrypt(&reqctx->fallback_req);
 
 	return err;
 
···
 {
 	struct ablk_ctx *ablkctx = ABLK_CTX(c_ctx(cipher));
 
-	crypto_sync_skcipher_clear_flags(ablkctx->sw_cipher,
+	crypto_skcipher_clear_flags(ablkctx->sw_cipher,
 				CRYPTO_TFM_REQ_MASK);
-	crypto_sync_skcipher_set_flags(ablkctx->sw_cipher,
+	crypto_skcipher_set_flags(ablkctx->sw_cipher,
 				cipher->base.crt_flags & CRYPTO_TFM_REQ_MASK);
-	return crypto_sync_skcipher_setkey(ablkctx->sw_cipher, key, keylen);
+	return crypto_skcipher_setkey(ablkctx->sw_cipher, key, keylen);
 }
 
 static int chcr_aes_cbc_setkey(struct crypto_skcipher *cipher,
···
 				      req);
 		memcpy(req->iv, reqctx->init_iv, IV);
 		atomic_inc(&adap->chcr_stats.fallback);
-		err = chcr_cipher_fallback(ablkctx->sw_cipher,
-				     req->base.flags,
-				     req->src,
-				     req->dst,
-				     req->cryptlen,
-				     req->iv,
-				     reqctx->op);
+		err = chcr_cipher_fallback(ablkctx->sw_cipher, req, req->iv,
+					   reqctx->op);
 		goto complete;
 	}
 
···
 		chcr_cipher_dma_unmap(&ULD_CTX(c_ctx(tfm))->lldi.pdev->dev,
 				      req);
 fallback:       atomic_inc(&adap->chcr_stats.fallback);
-		err = chcr_cipher_fallback(ablkctx->sw_cipher,
-					   req->base.flags,
-					   req->src,
-					   req->dst,
-					   req->cryptlen,
+		err = chcr_cipher_fallback(ablkctx->sw_cipher, req,
 					   subtype ==
 					   CRYPTO_ALG_SUB_TYPE_CTR_RFC3686 ?
 					   reqctx->iv : req->iv,
···
 	struct chcr_context *ctx = crypto_skcipher_ctx(tfm);
 	struct ablk_ctx *ablkctx = ABLK_CTX(ctx);
 
-	ablkctx->sw_cipher = crypto_alloc_sync_skcipher(alg->base.cra_name, 0,
+	ablkctx->sw_cipher = crypto_alloc_skcipher(alg->base.cra_name, 0,
 				CRYPTO_ALG_NEED_FALLBACK);
 	if (IS_ERR(ablkctx->sw_cipher)) {
 		pr_err("failed to allocate fallback for %s\n", alg->base.cra_name);
 		return PTR_ERR(ablkctx->sw_cipher);
 	}
 	init_completion(&ctx->cbc_aes_aio_done);
-	crypto_skcipher_set_reqsize(tfm, sizeof(struct chcr_skcipher_req_ctx));
+	crypto_skcipher_set_reqsize(tfm, sizeof(struct chcr_skcipher_req_ctx) +
+					 crypto_skcipher_reqsize(ablkctx->sw_cipher));
 
 	return chcr_device_init(ctx);
 }
···
 	/*RFC3686 initialises IV counter value to 1, rfc3686(ctr(aes))
 	 * cannot be used as fallback in chcr_handle_cipher_response
 	 */
-	ablkctx->sw_cipher = crypto_alloc_sync_skcipher("ctr(aes)", 0,
+	ablkctx->sw_cipher = crypto_alloc_skcipher("ctr(aes)", 0,
 				CRYPTO_ALG_NEED_FALLBACK);
 	if (IS_ERR(ablkctx->sw_cipher)) {
 		pr_err("failed to allocate fallback for %s\n", alg->base.cra_name);
 		return PTR_ERR(ablkctx->sw_cipher);
 	}
-	crypto_skcipher_set_reqsize(tfm, sizeof(struct chcr_skcipher_req_ctx));
+	crypto_skcipher_set_reqsize(tfm, sizeof(struct chcr_skcipher_req_ctx) +
+				    crypto_skcipher_reqsize(ablkctx->sw_cipher));
 	return chcr_device_init(ctx);
 }
 
···
 	struct chcr_context *ctx = crypto_skcipher_ctx(tfm);
 	struct ablk_ctx *ablkctx = ABLK_CTX(ctx);
 
-	crypto_free_sync_skcipher(ablkctx->sw_cipher);
+	crypto_free_skcipher(ablkctx->sw_cipher);
 }
 
 static int get_alg_config(struct algo_param *params,

drivers/crypto/chelsio/chcr_crypto.h

···
 }
 
 struct ablk_ctx {
-	struct crypto_sync_skcipher *sw_cipher;
+	struct crypto_skcipher *sw_cipher;
 	__be32 key_ctx_hdr;
 	unsigned int enckey_len;
 	unsigned char ciph_mode;
···
 	u8 init_iv[CHCR_MAX_CRYPTO_IV_LEN];
 	u16 txqidx;
 	u16 rxqidx;
+	struct skcipher_request fallback_req;	// keep at the end
 };
 
 struct chcr_alg_template {