Sasha Levin
2020-Jun-05 12:26 UTC
[PATCH AUTOSEL 4.14 3/8] net: check untrusted gso_size at kernel entry
From: Willem de Bruijn <willemb at google.com>
[ Upstream commit 6dd912f82680761d8fb6b1bb274a69d4c7010988 ]
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 9274124f023b ("net: stricter
validation of untrusted gso packets"), check gso_size at entry too.
Fixes: bfd5f4a3d605 ("packet: Add GSO/csum offload support.")
Reported-by: syzbot <syzkaller at googlegroups.com>
Signed-off-by: Willem de Bruijn <willemb at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
include/linux/virtio_net.h | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 44e20c4b5141..a16e0bdf7751 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -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.
@@ -90,17 +92,25 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
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;
--
2.25.1