Commit 4296adc3 authored Oct 02, 2020 by Guillaume Nault Committed by David S. Miller Oct 04, 2020

net/core: check length before updating Ethertype in skb_mpls_{push,pop}



Openvswitch allows to drop a packet's Ethernet header, therefore
skb_mpls_push() and skb_mpls_pop() might be called with ethernet=true
and mac_len=0. In that case the pointer passed to skb_mod_eth_type()
doesn't point to an Ethernet header and the new Ethertype is written at
unexpected locations.

Fix this by verifying that mac_len is big enough to contain an Ethernet
header.

Fixes: fa4e0f88 ("net/sched: fix corrupted L2 header with MPLS 'push' and 'pop' actions")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Acked-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f4544e53

net/core/skbuff.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -5622,7 +5622,7 @@ int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,
		lse->label_stack_entry = mpls_lse;
		skb_postpush_rcsum(skb, lse, MPLS_HLEN);

		if (ethernet)
		if (ethernet && mac_len >= ETH_HLEN)
		skb_mod_eth_type(skb, eth_hdr(skb), mpls_proto);
		skb->protocol = mpls_proto;

		@@ -5662,7 +5662,7 @@ int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len,
		skb_reset_mac_header(skb);
		skb_set_network_header(skb, mac_len);

		if (ethernet) {
		if (ethernet && mac_len >= ETH_HLEN) {
		struct ethhdr *hdr;

		/* use mpls_hdr() to get ethertype to account for VLANs. */

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