From: Weiming Shi process_sdp() declares union nf_inet_addr rtp_addr on the stack and passes it to the nf_nat_sip sdp_session hook after walking the SDP media descriptions. However rtp_addr is only initialized inside the media loop when a recognized media type with a non-zero port is found. If the SDP body contains no m= lines, only inactive media sections (m=audio 0 ...) or only unrecognized media types, rtp_addr is never assigned. Despite that, the function still calls hooks->sdp_session() with &rtp_addr, causing nf_nat_sdp_session() to format the stale stack value as an IP address and rewrite the SDP session owner and connection lines with it. With CONFIG_INIT_STACK_ALL_ZERO (default on most distributions) this results in the session-level o= and c= addresses being rewritten to 0.0.0.0 for inactive SDP sessions. Without stack auto-init the rewritten address is whatever happened to be on the stack. Fix this by pre-initializing rtp_addr from the session-level connection address (caddr) when available, and tracking via a have_rtp_addr flag whether any valid address was established. Skip the sdp_session hook entirely when no valid address exists. Fixes: 4ab9e64e5e3c ("[NETFILTER]: nf_nat_sip: split up SDP mangling") Reported-by: Xiang Mei Signed-off-by: Weiming Shi Signed-off-by: Florian Westphal --- net/netfilter/nf_conntrack_sip.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c index 20e57cf5c83a..939502ff7c87 100644 --- a/net/netfilter/nf_conntrack_sip.c +++ b/net/netfilter/nf_conntrack_sip.c @@ -1040,6 +1040,7 @@ static int process_sdp(struct sk_buff *skb, unsigned int protoff, unsigned int port; const struct sdp_media_type *t; int ret = NF_ACCEPT; + bool have_rtp_addr = false; hooks = rcu_dereference(nf_nat_sip_hooks); @@ -1056,8 +1057,11 @@ static int process_sdp(struct sk_buff *skb, unsigned int protoff, caddr_len = 0; if (ct_sip_parse_sdp_addr(ct, *dptr, sdpoff, *datalen, SDP_HDR_CONNECTION, SDP_HDR_MEDIA, - &matchoff, &matchlen, &caddr) > 0) + &matchoff, &matchlen, &caddr) > 0) { caddr_len = matchlen; + memcpy(&rtp_addr, &caddr, sizeof(rtp_addr)); + have_rtp_addr = true; + } mediaoff = sdpoff; for (i = 0; i < ARRAY_SIZE(sdp_media_types); ) { @@ -1091,9 +1095,11 @@ static int process_sdp(struct sk_buff *skb, unsigned int protoff, &matchoff, &matchlen, &maddr) > 0) { maddr_len = matchlen; memcpy(&rtp_addr, &maddr, sizeof(rtp_addr)); - } else if (caddr_len) + have_rtp_addr = true; + } else if (caddr_len) { memcpy(&rtp_addr, &caddr, sizeof(rtp_addr)); - else { + have_rtp_addr = true; + } else { nf_ct_helper_log(skb, ct, "cannot parse SDP message"); return NF_DROP; } @@ -1125,7 +1131,7 @@ static int process_sdp(struct sk_buff *skb, unsigned int protoff, /* Update session connection and owner addresses */ hooks = rcu_dereference(nf_nat_sip_hooks); - if (hooks && ct->status & IPS_NAT_MASK) + if (hooks && ct->status & IPS_NAT_MASK && have_rtp_addr) ret = hooks->sdp_session(skb, protoff, dataoff, dptr, datalen, sdpoff, &rtp_addr); -- 2.52.0