crypto: stm32 - Fix empty message processing

Change the emptymsg check in stm32_hash_copy_hash to rely on whether
we have any existing hash state, rather than whether this particular
update request is empty.

Also avoid computing the hash for empty messages as this could hang.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/stm32/stm32-hash.c

@@ -95,6 +95,7 @@
 #define HASH_FLAGS_SHA1			BIT(19)
 #define HASH_FLAGS_SHA224		BIT(20)
 #define HASH_FLAGS_SHA256		BIT(21)
+#define HASH_FLAGS_EMPTY		BIT(22)
 #define HASH_FLAGS_HMAC			BIT(23)
 
 #define HASH_OP_UPDATE			1
@@ -310,13 +311,6 @@ static void stm32_hash_write_ctrl(struct stm32_hash_dev *hdev, int bufcnt)
 				reg |= HASH_CR_LKEY;
 		}
 
-		/*
-		 * On the Ux500 we need to set a special flag to indicate that
-		 * the message is zero length.
-		 */
-		if (hdev->pdata->ux500 && bufcnt == 0)
-			reg |= HASH_CR_UX500_EMPTYMSG;
-
 		if (!hdev->polled)
 			stm32_hash_write(hdev, HASH_IMR, HASH_DCIE);
 
@@ -366,13 +360,23 @@ static void stm32_hash_append_sg(struct stm32_hash_request_ctx *rctx)
 static int stm32_hash_xmit_cpu(struct stm32_hash_dev *hdev,
 			       const u8 *buf, size_t length, int final)
 {
+	struct stm32_hash_request_ctx *rctx = ahash_request_ctx(hdev->req);
+	struct stm32_hash_state *state = &rctx->state;
 	unsigned int count, len32;
 	const u32 *buffer = (const u32 *)buf;
 	u32 reg;
 
-	if (final)
+	if (final) {
 		hdev->flags |= HASH_FLAGS_FINAL;
 
+		/* Do not process empty messages if hw is buggy. */
+		if (!(hdev->flags & HASH_FLAGS_INIT) && !length &&
+		    hdev->pdata->broken_emptymsg) {
+			state->flags |= HASH_FLAGS_EMPTY;
+			return 0;
+		}
+	}
+
 	len32 = DIV_ROUND_UP(length, sizeof(u32));
 
 	dev_dbg(hdev->dev, "%s: length: %zd, final: %x len32 %i\n",
@@ -827,7 +831,7 @@ static void stm32_hash_copy_hash(struct ahash_request *req)
 	__be32 *hash = (void *)rctx->digest;
 	unsigned int i, hashsize;
 
-	if (hdev->pdata->broken_emptymsg && !req->nbytes)
+	if (hdev->pdata->broken_emptymsg && (state->flags & HASH_FLAGS_EMPTY))
 		return stm32_hash_emptymsg_fallback(req);
 
 	switch (state->flags & HASH_FLAGS_ALGO_MASK) {