Currently we do not validate the vector length before calling get_user_pages_fast(), host stack would be easily overflowed by malicious guest driver who give us a descriptor with length greater than MAX_SKB_FRAGS. Solve this problem by checking the free entries before trying to pin user pages. Signed-off-by: Jason Wang --- drivers/net/macvtap.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c index 7cb2684..d197a78 100644 --- a/drivers/net/macvtap.c +++ b/drivers/net/macvtap.c @@ -527,6 +527,8 @@ static int zerocopy_sg_from_iovec(struct sk_buff *skb, const struct iovec *from, } base = (unsigned long)from->iov_base + offset1; size = ((base & ~PAGE_MASK) + len + ~PAGE_MASK) >> PAGE_SHIFT; + if (i + size >= MAX_SKB_FRAGS) + return -EFAULT; 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))