From 7c68d1a6b4db9012790af7ac0f0fdc0d2083422a Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 18 Jan 2018 19:59:19 -0800 Subject: [PATCH] net: qdisc_pkt_len_init() should be more robust Without proper validation of DODGY packets, we might very well feed qdisc_pkt_len_init() with invalid GSO packets. tcp_hdrlen() might access out-of-bound data, so let's use skb_header_pointer() and proper checks. Whole story is described in commit d0c081b49137 ("flow_dissector: properly cap thoff field") We have the goal of validating DODGY packets earlier in the stack, so we might very well revert this fix in the future. Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Cc: Jason Wang Reported-by: syzbot+9da69ebac7dddd804552@syzkaller.appspotmail.com Acked-by: Jason Wang Signed-off-by: David S. Miller --- net/core/dev.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/net/core/dev.c b/net/core/dev.c index 0e0ba36..613fb40 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3151,10 +3151,21 @@ static void qdisc_pkt_len_init(struct sk_buff *skb) hdr_len = skb_transport_header(skb) - skb_mac_header(skb); /* + transport layer */ - if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) - hdr_len += tcp_hdrlen(skb); - else - hdr_len += sizeof(struct udphdr); + if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) { + const struct tcphdr *th; + struct tcphdr _tcphdr; + + th = skb_header_pointer(skb, skb_transport_offset(skb), + sizeof(_tcphdr), &_tcphdr); + if (likely(th)) + hdr_len += __tcp_hdrlen(th); + } else { + struct udphdr _udphdr; + + if (skb_header_pointer(skb, skb_transport_offset(skb), + sizeof(_udphdr), &_udphdr)) + hdr_len += sizeof(struct udphdr); + } if (shinfo->gso_type & SKB_GSO_DODGY) gso_segs = DIV_ROUND_UP(skb->len - hdr_len, -- 2.7.4