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

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when 'act_mpls' is used to mangle the LSE, the current value is read from
the packet dereferencing 4 bytes at mpls_hdr(): ensure that the label is
contained in the skb "linear" area.

Found by code inspection.

v2:
 - use MPLS_HLEN instead of sizeof(new_lse), thanks to Jakub Kicinski

Fixes: 2a2ea50870 ("net: sched: add mpls manipulation actions to TC")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Guillaume Nault <gnault@redhat.com>
Link: https://lore.kernel.org/r/3243506cba43d14858f3bd21ee0994160e44d64a.1606987058.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Davide Caratti 2020-12-03 10:37:52 +01:00 committed by Jakub Kicinski
parent 43c13605ba
commit 9608fa6530
1 changed files with 3 additions and 0 deletions
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3
net/sched/act_mpls.c
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@ -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) + MPLS_HLEN))
goto drop;
new_lse = tcf_mpls_get_lse(mpls_hdr(skb), p, false);
if (skb_mpls_update_lse(skb, new_lse))
goto drop;