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Commit d8dee188 authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
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net: qdisc_pkt_len_init() should be more robust 




[ Upstream commit 7c68d1a6b4db9012790af7ac0f0fdc0d2083422a ]

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: default avatarEric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Jason Wang <jasowang@redhat.com>
Reported-by: default avatar <syzbot+9da69ebac7dddd804552@syzkaller.appspotmail.com>
Acked-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent eaf3179d

net/core/dev.c

+15 −4
Original line number Diff line number Diff line
@@ -2772,10 +2772,21 @@ 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

		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,