crypto: virtio: Fix src/dst scatterlist calculation in __virtio_crypto_skcipher_do_req()

The system will crash when the users insmod crypto/tcrypt.ko with mode=38
( testing "cts(cbc(aes))" ).

Usually the next entry of one sg will be @sg@ + 1, but if this sg element
is part of a chained scatterlist, it could jump to the start of a new
scatterlist array. Fix it by sg_next() on calculation of src/dst
scatterlist.

Fixes: dbaf0624ffa5 ("crypto: add virtio-crypto driver")
Reported-by: LABBE Corentin <clabbe@baylibre.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: virtualization@lists.linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200123101000.GB24255@Red
Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Link: https://lore.kernel.org/r/20200602070501.2023-2-longpeng2@huawei.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/crypto/virtio/virtio_crypto_algs.c b/drivers/crypto/virtio/virtio_crypto_algs.c
index fd045e64972a5b95542f8c474b57751f4b611f8a..5f82435630094ef2ad4001424bcb2c92f3b7732a 100644 (file)
--- a/drivers/crypto/virtio/virtio_crypto_algs.c
+++ b/drivers/crypto/virtio/virtio_crypto_algs.c
@@ -350,13 +350,18 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
        int err;
        unsigned long flags;
        struct scatterlist outhdr, iv_sg, status_sg, **sgs;
-       int i;
        u64 dst_len;
        unsigned int num_out = 0, num_in = 0;
        int sg_total;
        uint8_t *iv;
+       struct scatterlist *sg;
 
        src_nents = sg_nents_for_len(req->src, req->cryptlen);
+       if (src_nents < 0) {
+               pr_err("Invalid number of src SG.\n");
+               return src_nents;
+       }
+
        dst_nents = sg_nents(req->dst);
 
        pr_debug("virtio_crypto: Number of sgs (src_nents: %d, dst_nents: %d)\n",
@@ -442,12 +447,12 @@ __virtio_crypto_skcipher_do_req(struct virtio_crypto_sym_request *vc_sym_req,
        vc_sym_req->iv = iv;
 
        /* Source data */
-       for (i = 0; i < src_nents; i++)
-               sgs[num_out++] = &req->src[i];
+       for (sg = req->src; src_nents; sg = sg_next(sg), src_nents--)
+               sgs[num_out++] = sg;
 
        /* Destination data */
-       for (i = 0; i < dst_nents; i++)
-               sgs[num_out + num_in++] = &req->dst[i];
+       for (sg = req->dst; sg; sg = sg_next(sg))
+               sgs[num_out + num_in++] = sg;
 
        /* Status */
        sg_init_one(&status_sg, &vc_req->status, sizeof(vc_req->status));