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net: skbuff: ensure LSE is pullable before decrementing the MPLS ttl 

skb_mpls_dec_ttl() reads the LSE without ensuring that it is contained in
the skb "linear" area. Fix this calling pskb_may_pull() before reading the
current ttl.

Found by code inspection.

Fixes: 2a2ea50870 ("net: sched: add mpls manipulation actions to TC")
Reported-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/53659f28be8bc336c113b5254dc637cc76bbae91.1606987074.git.dcaratti@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
zero-sugar-mainline-defconfig
Davide Caratti 2020-12-03 10:58:21 +01:00 committed by Jakub Kicinski
parent 6392b5b28e
commit 13de4ed9e3
1 changed files with 3 additions and 0 deletions
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3
net/core/skbuff.c
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@ -5786,6 +5786,9 @@ int skb_mpls_dec_ttl(struct sk_buff *skb)
if (unlikely(!eth_p_mpls(skb->protocol)))
return -EINVAL;
if (!pskb_may_pull(skb, skb_network_offset(skb) + MPLS_HLEN))
return -ENOMEM;
lse = be32_to_cpu(mpls_hdr(skb)->label_stack_entry);
ttl = (lse & MPLS_LS_TTL_MASK) >> MPLS_LS_TTL_SHIFT;
if (!--ttl)