From: Willem de Bruijn willemb@google.com
[ Upstream commit 9274124f023b5c56dc4326637d4f787968b03607 ]
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/virtio_net.h | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-)
--- 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( 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 +67,20 @@ static inline int virtio_net_hdr_to_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 keys; + if (!skb->protocol) virtio_net_hdr_set_proto(skb, hdr); retry: - skb_probe_transport_header(skb, -1); - if (!skb_transport_header_was_set(skb)) { + if (!skb_flow_dissect_flow_keys(skb, &keys, 0)) { /* UFO does not specify ipv4 or 6: try both */ if (gso_type & SKB_GSO_UDP && skb->protocol == htons(ETH_P_IP)) { @@ -75,6 +89,12 @@ 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); } }