From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Rafal Kupka" , "Pablo Neira Ayuso" Date: Sun, 11 Feb 2018 04:20:06 +0000 Message-ID: Subject: [PATCH 3.2 61/79] netfilter: xt_TCPOPTSTRIP: fix possible mangling beyond packet boundary In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.2.99-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Pablo Neira Ayuso commit bc6bcb59dd7c184d229f9e86d08aa56059938a4c upstream. This target assumes that tcph->doff is well-formed, that may be well not the case. Add extra sanity checkings to avoid possible crash due to read/write out of the real packet boundary. After this patch, the default action on malformed TCP packets is to drop them. Moreover, fragments are skipped. Reported-by: Rafal Kupka Signed-off-by: Pablo Neira Ayuso Signed-off-by: Ben Hutchings --- net/netfilter/xt_TCPOPTSTRIP.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) --- a/net/netfilter/xt_TCPOPTSTRIP.c +++ b/net/netfilter/xt_TCPOPTSTRIP.c @@ -30,17 +30,28 @@ static inline unsigned int optlen(const static unsigned int tcpoptstrip_mangle_packet(struct sk_buff *skb, - const struct xt_tcpoptstrip_target_info *info, + const struct xt_action_param *par, unsigned int tcphoff, unsigned int minlen) { + const struct xt_tcpoptstrip_target_info *info = par->targinfo; unsigned int optl, i, j; struct tcphdr *tcph; u_int16_t n, o; u_int8_t *opt; + int len; + + /* This is a fragment, no TCP header is available */ + if (par->fragoff != 0) + return XT_CONTINUE; if (!skb_make_writable(skb, skb->len)) return NF_DROP; + len = skb->len - tcphoff; + if (len < (int)sizeof(struct tcphdr) || + tcp_hdr(skb)->doff * 4 > len) + return NF_DROP; + tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); opt = (u_int8_t *)tcph; @@ -76,7 +87,7 @@ tcpoptstrip_mangle_packet(struct sk_buff static unsigned int tcpoptstrip_tg4(struct sk_buff *skb, const struct xt_action_param *par) { - return tcpoptstrip_mangle_packet(skb, par->targinfo, ip_hdrlen(skb), + return tcpoptstrip_mangle_packet(skb, par, ip_hdrlen(skb), sizeof(struct iphdr) + sizeof(struct tcphdr)); } @@ -93,7 +104,7 @@ tcpoptstrip_tg6(struct sk_buff *skb, con if (tcphoff < 0) return NF_DROP; - return tcpoptstrip_mangle_packet(skb, par->targinfo, tcphoff, + return tcpoptstrip_mangle_packet(skb, par, tcphoff, sizeof(*ipv6h) + sizeof(struct tcphdr)); } #endif