From ba203b92a829c8aaf8763c76034e21e687b1b9bf Mon Sep 17 00:00:00 2001 From: Davide Caratti Date: Thu, 3 Dec 2020 10:58:21 +0100 Subject: [PATCH] net: skbuff: ensure LSE is pullable before decrementing the MPLS ttl [ Upstream commit 13de4ed9e3a9ccbe54d05f7d5c773f69ecaf6c64 ] 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: 2a2ea50870ba ("net: sched: add mpls manipulation actions to TC") Reported-by: Marcelo Ricardo Leitner Signed-off-by: Davide Caratti Link: https://lore.kernel.org/r/53659f28be8bc336c113b5254dc637cc76bbae91.1606987074.git.dcaratti@redhat.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/core/skbuff.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 5fd6633bfa5b..a0486dcf5425 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5618,6 +5618,9 @@ 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)