[PATCH net] net/sched: act_mpls: ensure LSE is pullable before reading it

[Davide Caratti]

when 'act_mpls' is used to mangle the LSE, the current value is read from
the packet with mpls_hdr(): ensure that the label is contained in the skb
"linear" area.

Found by code inspection.

Fixes: 2a2ea50870ba ("net: sched: add mpls manipulation actions to TC")
Signed-off-by: Davide Caratti <dcara...@redhat.com>
---
 net/sched/act_mpls.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/sched/act_mpls.c b/net/sched/act_mpls.c
index 5c7456e5b5cf..03138ad59e9b 100644
--- a/net/sched/act_mpls.c
+++ b/net/sched/act_mpls.c
@@ -105,6 +105,9 @@ static int tcf_mpls_act(struct sk_buff *skb, const struct 
tc_action *a,
                        goto drop;
                break;
        case TCA_MPLS_ACT_MODIFY:
+               if (!pskb_may_pull(skb,
+                                  skb_network_offset(skb) + sizeof(new_lse)))
+                       goto drop;
                new_lse = tcf_mpls_get_lse(mpls_hdr(skb), p, false);
                if (skb_mpls_update_lse(skb, new_lse))
                        goto drop;
-- 
2.28.0