| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.4 79/85] net/core: check length before updating Ethertype in skb_mpls_{push,pop} | Date | Mon, 12 Oct 2020 15:27:42 +0200 |
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From: Guillaume Nault <gnault@redhat.com>
commit 4296adc3e32f5d544a95061160fe7e127be1b9ff upstream.
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- net/core/skbuff.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5515,7 +5515,7 @@ 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; @@ -5555,7 +5555,7 @@ 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. */
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