This is a note to let you know that I've just added the patch titled net/core: check length before updating Ethertype in skb_mpls_{push,pop} to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-core-check-length-before-updating-ethertype-in-skb_mpls_-push-pop.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 4296adc3e32f5d544a95061160fe7e127be1b9ff Mon Sep 17 00:00:00 2001 From: Guillaume Nault <gnault@xxxxxxxxxx> Date: Fri, 2 Oct 2020 21:53:08 +0200 Subject: net/core: check length before updating Ethertype in skb_mpls_{push,pop} From: Guillaume Nault <gnault@xxxxxxxxxx> 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@xxxxxxxxxx> Acked-by: Davide Caratti <dcaratti@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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. */ Patches currently in stable-queue which might be from gnault@xxxxxxxxxx are queue-5.4/net-core-check-length-before-updating-ethertype-in-skb_mpls_-push-pop.patch