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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 d0c081b491 ("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 <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Jason Wang <jasowang@redhat.com>
Reported-by: syzbot+9da69ebac7dddd804552@syzkaller.appspotmail.com
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-01-18 19:59:19 -08:00 committed by David S. Miller
parent 18b0affaf4
commit 7c68d1a6b4
1 changed files with 15 additions and 4 deletions
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19
net/core/dev.c
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@ -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,