From: Pablo Neira Ayuso Date: Fri, 26 Jun 2026 11:24:49 +0000 (+0200) Subject: netfilter: nf_conntrack_sip: validate skb_dst() before accessing it X-Git-Tag: v7.2-rc2~22^2~2^2~5 X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=e5e24a365a5e024efef63cc49abb345fbd4852c5;p=thirdparty%2Flinux.git netfilter: nf_conntrack_sip: validate skb_dst() before accessing it tc ingress and openvswitch do not guarantee routing information to be available. These subsystems use the conntrack helper infrastructure, and the SIP helper relies on the skb_dst() to be present if sip_external_media is set to 1 (which is disabled by default as a module parameter). This effectively disables the sip_external_media toggle for these subsystems without resulting in a crash. Fixes: cae3a2627520 ("openvswitch: Allow attaching helpers to ct action") Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct") Cc: stable@vger.kernel.org Reported-by: Ren Wei Signed-off-by: Pablo Neira Ayuso Signed-off-by: Florian Westphal --- diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c index 5ec3a4a4bbd7..f3f90a866338 100644 --- a/net/netfilter/nf_conntrack_sip.c +++ b/net/netfilter/nf_conntrack_sip.c @@ -956,7 +956,6 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, unsigned int protoff, return NF_ACCEPT; saddr = &ct->tuplehash[!dir].tuple.src.u3; } else if (sip_external_media) { - struct net_device *dev = skb_dst(skb)->dev; struct dst_entry *dst = NULL; struct flowi fl; @@ -978,7 +977,11 @@ static int set_expected_rtp_rtcp(struct sk_buff *skb, unsigned int protoff, * through the same interface as the signalling peer. */ if (dst) { - bool external_media = (dst->dev == dev); + const struct dst_entry *this_dst = skb_dst(skb); + bool external_media = false; + + if (this_dst && dst->dev == this_dst->dev) + external_media = true; dst_release(dst); if (external_media)