Linux Virtualization - Jun 2020 - [PATCH 4.19 066/267] crypto: virtio: Fix dest length calculation in __virtio_crypto_skcipher_do_req()

From: Longpeng(Mike) <longpeng2 at huawei.com>

[ Upstream commit d90ca42012db2863a9a30b564a2ace6016594bda ]

The src/dst length is not aligned with AES_BLOCK_SIZE(which is 16) in some
testcases in tcrypto.ko.

For example, the src/dst length of one of cts(cbc(aes))'s testcase is 17,
the
crypto_virtio driver will set @src_data_len=16 but @dst_data_len=17 in this
case and get a wrong at then end.

  SRC: pp pp pp pp pp pp pp pp pp pp pp pp pp pp pp pp pp (17 bytes)
  EXP: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc pp (17 bytes)
  DST: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 00 (pollute the last
bytes)
  (pp: plaintext  cc:ciphertext)

Fix this issue by limit the length of dest buffer.

Fixes: dbaf0624ffa5 ("crypto: add virtio-crypto driver")
Cc: Gonglei <arei.gonglei at huawei.com>
Cc: Herbert Xu <herbert at gondor.apana.org.au>
Cc: "Michael S. Tsirkin" <mst at redhat.com>
Cc: Jason Wang <jasowang at redhat.com>
Cc: "David S. Miller" <davem at davemloft.net>
Cc: virtualization at lists.linux-foundation.org
Cc: linux-kernel at vger.kernel.org
Cc: stable at vger.kernel.org
Signed-off-by: Longpeng(Mike) <longpeng2 at huawei.com>
Link: https://lore.kernel.org/r/20200602070501.2023-4-longpeng2 at huawei.com
Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/crypto/virtio/virtio_crypto_algs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/crypto/virtio/virtio_crypto_algs.c
b/drivers/crypto/virtio/virtio_crypto_algs.c
index e9a8485c4929..ab4700e4b409 100644
--- a/drivers/crypto/virtio/virtio_crypto_algs.c
+++ b/drivers/crypto/virtio/virtio_crypto_algs.c
@@ -424,6 +424,7 @@ __virtio_crypto_ablkcipher_do_req(struct
virtio_crypto_sym_request *vc_sym_req,
 		goto free;
 	}
 
+	dst_len = min_t(unsigned int, req->nbytes, dst_len);
 	pr_debug("virtio_crypto: src_len: %u, dst_len: %llu\n",
 			req->nbytes, dst_len);
 
-- 
2.25.1