crypto: ahash - Fix crypto_ahash_import with partial block data

Restore the partial block buffer in crypto_ahash_import by copying
it.  Check whether the partial block buffer exceeds the maximum
size and return -EOVERFLOW if it does.

Zero the partial block buffer in crypto_ahash_import_core.

Reported-by: T Pratham <t-pratham@ti.com>
Tested-by: T Pratham <t-pratham@ti.com>
Fixes: 9d7a0ab ("crypto: ahash - Handle partial blocks in API")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: herbertx

crypto/ahash.c

@@ -661,6 +661,12 @@ int crypto_ahash_import_core(struct ahash_request *req, const void *in)
 						in);
 	if (crypto_ahash_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
 		return -ENOKEY;
+	if (crypto_ahash_block_only(tfm)) {
+		unsigned int reqsize = crypto_ahash_reqsize(tfm);
+		u8 *buf = ahash_request_ctx(req);
+
+		buf[reqsize - 1] = 0;
+	}
 	return crypto_ahash_alg(tfm)->import_core(req, in);
 }
 EXPORT_SYMBOL_GPL(crypto_ahash_import_core);
@@ -674,10 +680,14 @@ int crypto_ahash_import(struct ahash_request *req, const void *in)
 	if (crypto_ahash_get_flags(tfm) & CRYPTO_TFM_NEED_KEY)
 		return -ENOKEY;
 	if (crypto_ahash_block_only(tfm)) {
+		unsigned int plen = crypto_ahash_blocksize(tfm) + 1;
 		unsigned int reqsize = crypto_ahash_reqsize(tfm);
+		unsigned int ss = crypto_ahash_statesize(tfm);
 		u8 *buf = ahash_request_ctx(req);
 
-		buf[reqsize - 1] = 0;
+		memcpy(buf + reqsize - plen, in + ss - plen, plen);
+		if (buf[reqsize - 1] >= plen)
+			return -EOVERFLOW;
 	}
 	return crypto_ahash_alg(tfm)->import(req, in);
 }