Commit b92946e2 authored by Jason Wang's avatar Jason Wang Committed by Michael S. Tsirkin
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macvtap: zerocopy: validate vectors before building skb



There're several reasons that the vectors need to be validated:

- Return error when caller provides vectors whose num is greater than UIO_MAXIOV.
- Linearize part of skb when userspace provides vectors grater than MAX_SKB_FRAGS.
- Return error when userspace provides vectors whose total length may exceed
- MAX_SKB_FRAGS * PAGE_SIZE.
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 01d6657b
......@@ -529,9 +529,10 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from,
}
base = (unsigned long)from->iov_base + offset;
size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT;
if (i + size > MAX_SKB_FRAGS)
return -EMSGSIZE;
num_pages = get_user_pages_fast(base, size, 0, &page[i]);
if ((num_pages != size) ||
(num_pages > MAX_SKB_FRAGS - skb_shinfo(skb)->nr_frags)) {
if (num_pages != size) {
for (i = 0; i < num_pages; i++)
put_page(page[i]);
return -EFAULT;
......@@ -651,7 +652,7 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
int err;
struct virtio_net_hdr vnet_hdr = { 0 };
int vnet_hdr_len = 0;
int copylen;
int copylen = 0;
bool zerocopy = false;
if (q->flags & IFF_VNET_HDR) {
......@@ -680,15 +681,31 @@ static ssize_t macvtap_get_user(struct macvtap_queue *q, struct msghdr *m,
if (unlikely(len < ETH_HLEN))
goto err;
err = -EMSGSIZE;
if (unlikely(count > UIO_MAXIOV))
goto err;
if (m && m->msg_control && sock_flag(&q->sk, SOCK_ZEROCOPY))
zerocopy = true;
if (zerocopy) {
/* Userspace may produce vectors with count greater than
* MAX_SKB_FRAGS, so we need to linearize parts of the skb
* to let the rest of data to be fit in the frags.
*/
if (count > MAX_SKB_FRAGS) {
copylen = iov_length(iv, count - MAX_SKB_FRAGS);
if (copylen < vnet_hdr_len)
copylen = 0;
else
copylen -= vnet_hdr_len;
}
/* There are 256 bytes to be copied in skb, so there is enough
* room for skb expand head in case it is used.
* The rest buffer is mapped from userspace.
*/
copylen = vnet_hdr.hdr_len;
if (copylen < vnet_hdr.hdr_len)
copylen = vnet_hdr.hdr_len;
if (!copylen)
copylen = GOODCOPY_LEN;
} else
......
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