Commit 6dd912f8 authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

net: check untrusted gso_size at kernel entry 



Syzkaller again found a path to a kernel crash through bad gso input:
a packet with gso size exceeding len.

These packets are dropped in tcp_gso_segment and udp[46]_ufo_fragment.
But they may affect gso size calculations earlier in the path.

Now that we have thlen as of commit 9274124f ("net: stricter
validation of untrusted gso packets"), check gso_size at entry too.

Fixes: bfd5f4a3 ("packet: Add GSO/csum offload support.")
Reported-by: default avatarsyzbot <syzkaller@googlegroups.com>
Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0a82e230

include/linux/virtio_net.h

+12 −2
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, 
{

	unsigned int gso_type = 0;

	unsigned int thlen = 0;

	unsigned int p_off = 0;

	unsigned int ip_proto;



	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
@@ -68,7 +69,8 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, 
		if (!skb_partial_csum_set(skb, start, off))

			return -EINVAL;



		if (skb_transport_offset(skb) + thlen > skb_headlen(skb))

		p_off = skb_transport_offset(skb) + thlen;

		if (p_off > skb_headlen(skb))

			return -EINVAL;

	} else {

		/* gso packets without NEEDS_CSUM do not set transport_offset.
@@ -92,17 +94,25 @@ retry: 
				return -EINVAL;

			}



			if (keys.control.thoff + thlen > skb_headlen(skb) ||

			p_off = keys.control.thoff + thlen;

			if (p_off > skb_headlen(skb) ||

			    keys.basic.ip_proto != ip_proto)

				return -EINVAL;



			skb_set_transport_header(skb, keys.control.thoff);

		} else if (gso_type) {

			p_off = thlen;

			if (p_off > skb_headlen(skb))

				return -EINVAL;

		}

	}



	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {

		u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size);



		if (skb->len - p_off <= gso_size)

			return -EINVAL;



		skb_shinfo(skb)->gso_size = gso_size;

		skb_shinfo(skb)->gso_type = gso_type;

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