| Message ID | 71ec98d51cc4aab7615061336fb1498ad16cda30.1601667845.git.gnault@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [net] net/core: check length before updating Ethertype in skb_mpls_{push,pop} | expand |
On Fri, 2020-10-02 at 21:53 +0200, Guillaume Nault wrote: > 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> > --- > Notes: > - Found by code inspection. > - Using commit fa4e0f8855fc for the Fixes tag because mac_len is > needed for the test. The problem probably exists since openvswitch > can pop the Ethernet header though. > > net/core/skbuff.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) Acked-by: Davide Caratti <dcaratti@redhat.com> thanks!
On Fri, 2020-10-02 at 21:53 +0200, Guillaume Nault wrote: > 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> Is this check redundant. I believe Openvswitch already takes care of it ?
From: "Varghese, Martin (Nokia - IN/Bangalore)" <martin.varghese@nokia.com> Date: Sun, 4 Oct 2020 14:50:58 +0000 > Is this check redundant. I believe Openvswitch already takes care of it ? Openvswitch isn't the only user of these skb_mpls_*() helpers.
From: Guillaume Nault <gnault@redhat.com> Date: Fri, 2 Oct 2020 21:53:08 +0200 > 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> Applied and queued up for -stable, thanks.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 6faf73d6a0f7..2b48cb0cc684 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -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. */
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> --- Notes: - Found by code inspection. - Using commit fa4e0f8855fc for the Fixes tag because mac_len is needed for the test. The problem probably exists since openvswitch can pop the Ethernet header though. net/core/skbuff.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)