From b90efd2258749e04e1b3f71ef0d716f2ac2337e0 Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Thu, 7 Feb 2019 14:54:16 -0500 Subject: bpf: only adjust gso_size on bytestream protocols bpf_skb_change_proto and bpf_skb_adjust_room change skb header length. For GSO packets they adjust gso_size to maintain the same MTU. The gso size can only be safely adjusted on bytestream protocols. Commit d02f51cbcf12 ("bpf: fix bpf_skb_adjust_net/bpf_skb_proto_xlat to deal with gso sctp skbs") excluded SKB_GSO_SCTP. Since then type SKB_GSO_UDP_L4 has been added, whose contents are one gso_size unit per datagram. Also exclude these. Move from a blacklist to a whitelist check to future proof against additional such new GSO types, e.g., for fraglist based GRO. Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT") Signed-off-by: Willem de Bruijn Signed-off-by: Alexei Starovoitov --- include/linux/skbuff.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/skbuff.h') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 95d25b010a25..5a7a8b93a5ab 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -4212,6 +4212,12 @@ static inline bool skb_is_gso_sctp(const struct sk_buff *skb) return skb_shinfo(skb)->gso_type & SKB_GSO_SCTP; } +static inline bool skb_is_gso_tcp(const struct sk_buff *skb) +{ + return skb_is_gso(skb) && + skb_shinfo(skb)->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6); +} + static inline void skb_gso_reset(struct sk_buff *skb) { skb_shinfo(skb)->gso_size = 0; -- cgit v1.2.3 From d5be7f632bad0f489879eed0ff4b99bd7fe0b74c Mon Sep 17 00:00:00 2001 From: Willem de Bruijn Date: Fri, 15 Feb 2019 12:15:47 -0500 Subject: net: validate untrusted gso packets without csum offload Syzkaller again found a path to a kernel crash through bad gso input. By building an excessively large packet to cause an skb field to wrap. If VIRTIO_NET_HDR_F_NEEDS_CSUM was set this would have been dropped in skb_partial_csum_set. GSO packets that do not set checksum offload are suspicious and rare. Most callers of virtio_net_hdr_to_skb already pass them to skb_probe_transport_header. Move that test forward, change it to detect parse failure and drop packets on failure as those cleary are not one of the legitimate VIRTIO_NET_HDR_GSO types. Fixes: bfd5f4a3d605 ("packet: Add GSO/csum offload support.") Fixes: f43798c27684 ("tun: Allow GSO using virtio_net_hdr") Reported-by: syzbot Signed-off-by: Willem de Bruijn Reviewed-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/skbuff.h | 2 +- include/linux/virtio_net.h | 9 +++++++++ 2 files changed, 10 insertions(+), 1 deletion(-) (limited to 'include/linux/skbuff.h') diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 95d25b010a25..4c1c82a5678c 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2434,7 +2434,7 @@ static inline void skb_probe_transport_header(struct sk_buff *skb, if (skb_flow_dissect_flow_keys_basic(skb, &keys, NULL, 0, 0, 0, 0)) skb_set_transport_header(skb, keys.control.thoff); - else + else if (offset_hint >= 0) skb_set_transport_header(skb, offset_hint); } diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h index cb462f9ab7dd..71f2394abbf7 100644 --- a/include/linux/virtio_net.h +++ b/include/linux/virtio_net.h @@ -57,6 +57,15 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, if (!skb_partial_csum_set(skb, start, off)) 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_probe_transport_header(skb, -1); + if (!skb_transport_header_was_set(skb)) + return -EINVAL; + } } if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) { -- cgit v1.2.3