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

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
...@@ -31,6 +31,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, ...@@ -31,6 +31,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
{ {
unsigned int gso_type = 0; unsigned int gso_type = 0;
unsigned int thlen = 0; unsigned int thlen = 0;
unsigned int p_off = 0;
unsigned int ip_proto; unsigned int ip_proto;
if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) { 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, ...@@ -68,7 +69,8 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
if (!skb_partial_csum_set(skb, start, off)) if (!skb_partial_csum_set(skb, start, off))
return -EINVAL; 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; return -EINVAL;
} else { } else {
/* gso packets without NEEDS_CSUM do not set transport_offset. /* gso packets without NEEDS_CSUM do not set transport_offset.
...@@ -92,17 +94,25 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, ...@@ -92,17 +94,25 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
return -EINVAL; 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) keys.basic.ip_proto != ip_proto)
return -EINVAL; return -EINVAL;
skb_set_transport_header(skb, keys.control.thoff); 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) { if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size); 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_size = gso_size;
skb_shinfo(skb)->gso_type = gso_type; skb_shinfo(skb)->gso_type = gso_type;
......
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