crypto: s390 - Fix aes-xts parameter corruption

Some s390 crypto algorithms incorrectly use the crypto_tfm structure to
store private data. As the tfm can be shared among multiple threads, this
can result in data corruption.

This patch fixes aes-xts by moving the xts and pcc parameter blocks from
the tfm onto the stack (48 + 96 bytes).

Cc: stable@vger.kernel.org
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

arch/s390/crypto/aes_s390.c

@@ -55,8 +55,7 @@ struct pcc_param {
 
 struct s390_xts_ctx {
 	u8 key[32];
-	u8 xts_param[16];
-	struct pcc_param pcc;
+	u8 pcc_key[32];
 	long enc;
 	long dec;
 	int key_len;
@@ -591,7 +590,7 @@ static int xts_aes_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 		xts_ctx->enc = KM_XTS_128_ENCRYPT;
 		xts_ctx->dec = KM_XTS_128_DECRYPT;
 		memcpy(xts_ctx->key + 16, in_key, 16);
-		memcpy(xts_ctx->pcc.key + 16, in_key + 16, 16);
+		memcpy(xts_ctx->pcc_key + 16, in_key + 16, 16);
 		break;
 	case 48:
 		xts_ctx->enc = 0;
@@ -602,7 +601,7 @@ static int xts_aes_set_key(struct crypto_tfm *tfm, const u8 *in_key,
 		xts_ctx->enc = KM_XTS_256_ENCRYPT;
 		xts_ctx->dec = KM_XTS_256_DECRYPT;
 		memcpy(xts_ctx->key, in_key, 32);
-		memcpy(xts_ctx->pcc.key, in_key + 32, 32);
+		memcpy(xts_ctx->pcc_key, in_key + 32, 32);
 		break;
 	default:
 		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
@@ -621,29 +620,33 @@ static int xts_aes_crypt(struct blkcipher_desc *desc, long func,
 	unsigned int nbytes = walk->nbytes;
 	unsigned int n;
 	u8 *in, *out;
-	void *param;
+	struct pcc_param pcc_param;
+	struct {
+		u8 key[32];
+		u8 init[16];
+	} xts_param;
 
 	if (!nbytes)
 		goto out;
 
-	memset(xts_ctx->pcc.block, 0, sizeof(xts_ctx->pcc.block));
-	memset(xts_ctx->pcc.bit, 0, sizeof(xts_ctx->pcc.bit));
-	memset(xts_ctx->pcc.xts, 0, sizeof(xts_ctx->pcc.xts));
-	memcpy(xts_ctx->pcc.tweak, walk->iv, sizeof(xts_ctx->pcc.tweak));
-	param = xts_ctx->pcc.key + offset;
-	ret = crypt_s390_pcc(func, param);
+	memset(pcc_param.block, 0, sizeof(pcc_param.block));
+	memset(pcc_param.bit, 0, sizeof(pcc_param.bit));
+	memset(pcc_param.xts, 0, sizeof(pcc_param.xts));
+	memcpy(pcc_param.tweak, walk->iv, sizeof(pcc_param.tweak));
+	memcpy(pcc_param.key, xts_ctx->pcc_key, 32);
+	ret = crypt_s390_pcc(func, &pcc_param.key[offset]);
 	if (ret < 0)
 		return -EIO;
 
-	memcpy(xts_ctx->xts_param, xts_ctx->pcc.xts, 16);
-	param = xts_ctx->key + offset;
+	memcpy(xts_param.key, xts_ctx->key, 32);
+	memcpy(xts_param.init, pcc_param.xts, 16);
 	do {
 		/* only use complete blocks */
 		n = nbytes & ~(AES_BLOCK_SIZE - 1);
 		out = walk->dst.virt.addr;
 		in = walk->src.virt.addr;
 
-		ret = crypt_s390_km(func, param, out, in, n);
+		ret = crypt_s390_km(func, &xts_param.key[offset], out, in, n);
 		if (ret < 0 || ret != n)
 			return -EIO;