From: Guillaume Nault <gnault@redhat.com>
Date: Fri, 2 Oct 2020 21:53:08 +0200
Subject: net/core: check length before updating Ethertype in
skb_mpls_{push,pop}
Git-commit: 4296adc3e32f5d544a95061160fe7e127be1b9ff
Patch-mainline: 5.9
References: git-fixes
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: fa4e0f8855fc ("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>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
net/core/skbuff.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5509,7 +5509,7 @@ int skb_mpls_push(struct sk_buff *skb, _
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;
@@ -5549,7 +5549,7 @@ int skb_mpls_pop(struct sk_buff *skb, __
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. */