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net: check untrusted gso_size at kernel entry

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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 9274124f02 ("net: stricter
validation of untrusted gso packets"), check gso_size at entry too.

Fixes: bfd5f4a3d6 ("packet: Add GSO/csum offload support.")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Willem de Bruijn 2020-05-25 15:07:40 -04:00 committed by David S. Miller
parent 0a82e230c6
commit 6dd912f826
1 changed files with 12 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/linux/virtio_net.h
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@ -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;