From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	=?UTF-8?q?Lukas=20Johannes=20M=C3=B6ller?= <research@johannes-moeller.dev>,
	Florian Westphal <fw@strlen.de>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.12 394/460] netfilter: nf_conntrack_sip: fix Content-Length u32 truncation in sip_help_tcp()
Date: Mon, 23 Mar 2026 14:46:30 +0100
Message-ID: <20260323134536.248717309@linuxfoundation.org>
In-Reply-To: <20260323134526.647552166@linuxfoundation.org>
References: <20260323134526.647552166@linuxfoundation.org>
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6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lukas Johannes Möller <research@johannes-moeller.dev>

[ Upstream commit fbce58e719a17aa215c724473fd5baaa4a8dc57c ]

sip_help_tcp() parses the SIP Content-Length header with
simple_strtoul(), which returns unsigned long, but stores the result in
unsigned int clen.  On 64-bit systems, values exceeding UINT_MAX are
silently truncated before computing the SIP message boundary.

For example, Content-Length 4294967328 (2^32 + 32) is truncated to 32,
causing the parser to miscalculate where the current message ends.  The
loop then treats trailing data in the TCP segment as a second SIP
message and processes it through the SDP parser.

Fix this by changing clen to unsigned long to match the return type of
simple_strtoul(), and reject Content-Length values that exceed the
remaining TCP payload length.

Fixes: f5b321bd37fb ("netfilter: nf_conntrack_sip: add TCP support")
Signed-off-by: Lukas Johannes Möller <research@johannes-moeller.dev>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/netfilter/nf_conntrack_sip.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_sip.c b/net/netfilter/nf_conntrack_sip.c
index d0eac27f6ba03..657839a58782a 100644
--- a/net/netfilter/nf_conntrack_sip.c
+++ b/net/netfilter/nf_conntrack_sip.c
@@ -1534,11 +1534,12 @@ static int sip_help_tcp(struct sk_buff *skb, unsigned int protoff,
 {
 	struct tcphdr *th, _tcph;
 	unsigned int dataoff, datalen;
-	unsigned int matchoff, matchlen, clen;
+	unsigned int matchoff, matchlen;
 	unsigned int msglen, origlen;
 	const char *dptr, *end;
 	s16 diff, tdiff = 0;
 	int ret = NF_ACCEPT;
+	unsigned long clen;
 	bool term;
 
 	if (ctinfo != IP_CT_ESTABLISHED &&
@@ -1573,6 +1574,9 @@ static int sip_help_tcp(struct sk_buff *skb, unsigned int protoff,
 		if (dptr + matchoff == end)
 			break;
 
+		if (clen > datalen)
+			break;
+
 		term = false;
 		for (; end + strlen("\r\n\r\n") <= dptr + datalen; end++) {
 			if (end[0] == '\r' && end[1] == '\n' &&
-- 
2.51.0