Commit 13de4ed9 authored by Davide Caratti's avatar Davide Caratti Committed by Jakub Kicinski
Browse files

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: 2a2ea508 ("net: sched: add mpls manipulation actions to TC")
Reported-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: default avatarDavide Caratti <dcaratti@redhat.com>
Link: https://lore.kernel.org/r/53659f28be8bc336c113b5254dc637cc76bbae91.1606987074.git.dcaratti@redhat.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 6392b5b2

net/core/skbuff.c

+3 −0
Original line number Diff line number Diff line
@@ -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)