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authorWillem de Bruijn <willemb@google.com>2020-05-04 12:48:54 -0400
committerDavid S. Miller <davem@davemloft.net>2020-05-06 17:23:06 -0700
commit9274124f023b5c56dc4326637d4f787968b03607 (patch)
tree0f46c00bd05149b9747ab50c1e290a56fb7b5ee6
parent0cb7498f234e4e7d75187a8cae6c7c2053f2488a (diff)
net: stricter validation of untrusted gso packets
Syzkaller again found a path to a kernel crash through bad gso input: a packet with transport header extending beyond skb_headlen(skb). Tighten validation at kernel entry: - Verify that the transport header lies within the linear section. To avoid pulling linux/tcp.h, verify just sizeof tcphdr. tcp_gso_segment will call pskb_may_pull (th->doff * 4) before use. - Match the gso_type against the ip_proto found by the flow dissector. Fixes: bfd5f4a3d605 ("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>
-rw-r--r--include/linux/virtio_net.h26
1 files changed, 24 insertions, 2 deletions
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 0d1fe9297ac6..6f6ade63b04c 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -3,6 +3,8 @@
#define _LINUX_VIRTIO_NET_H
#include <linux/if_vlan.h>
+#include <uapi/linux/tcp.h>
+#include <uapi/linux/udp.h>
#include <uapi/linux/virtio_net.h>
static inline int virtio_net_hdr_set_proto(struct sk_buff *skb,
@@ -28,17 +30,25 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
bool little_endian)
{
unsigned int gso_type = 0;
+ unsigned int thlen = 0;
+ unsigned int ip_proto;
if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
case VIRTIO_NET_HDR_GSO_TCPV4:
gso_type = SKB_GSO_TCPV4;
+ ip_proto = IPPROTO_TCP;
+ thlen = sizeof(struct tcphdr);
break;
case VIRTIO_NET_HDR_GSO_TCPV6:
gso_type = SKB_GSO_TCPV6;
+ ip_proto = IPPROTO_TCP;
+ thlen = sizeof(struct tcphdr);
break;
case VIRTIO_NET_HDR_GSO_UDP:
gso_type = SKB_GSO_UDP;
+ ip_proto = IPPROTO_UDP;
+ thlen = sizeof(struct udphdr);
break;
default:
return -EINVAL;
@@ -57,16 +67,22 @@ 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))
+ return -EINVAL;
} else {
/* gso packets without NEEDS_CSUM do not set transport_offset.
* probe and drop if does not match one of the above types.
*/
if (gso_type && skb->network_header) {
+ struct flow_keys_basic keys;
+
if (!skb->protocol)
virtio_net_hdr_set_proto(skb, hdr);
retry:
- skb_probe_transport_header(skb);
- if (!skb_transport_header_was_set(skb)) {
+ if (!skb_flow_dissect_flow_keys_basic(NULL, skb, &keys,
+ NULL, 0, 0, 0,
+ 0)) {
/* UFO does not specify ipv4 or 6: try both */
if (gso_type & SKB_GSO_UDP &&
skb->protocol == htons(ETH_P_IP)) {
@@ -75,6 +91,12 @@ retry:
}
return -EINVAL;
}
+
+ if (keys.control.thoff + thlen > skb_headlen(skb) ||
+ keys.basic.ip_proto != ip_proto)
+ return -EINVAL;
+
+ skb_set_transport_header(skb, keys.control.thoff);
}
}