This is a note to let you know that I've just added the patch titled
netfilter: xt_TCPMSS: add more sanity tests on tcph->doff
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netfilter-xt_tcpmss-add-more-sanity-tests-on-tcph-doff.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 2638fd0f92d4397884fd991d8f4925cb3f081901 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Mon, 3 Apr 2017 10:55:11 -0700
Subject: netfilter: xt_TCPMSS: add more sanity tests on tcph->doff
From: Eric Dumazet <edumazet@xxxxxxxxxx>
commit 2638fd0f92d4397884fd991d8f4925cb3f081901 upstream.
Denys provided an awesome KASAN report pointing to an use
after free in xt_TCPMSS
I have provided three patches to fix this issue, either in xt_TCPMSS or
in xt_tcpudp.c. It seems xt_TCPMSS patch has the smallest possible
impact.
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reported-by: Denys Fedoryshchenko <nuclearcat@xxxxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/netfilter/xt_TCPMSS.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
--- a/net/netfilter/xt_TCPMSS.c
+++ b/net/netfilter/xt_TCPMSS.c
@@ -104,7 +104,7 @@ tcpmss_mangle_packet(struct sk_buff *skb
tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
tcp_hdrlen = tcph->doff * 4;
- if (len < tcp_hdrlen)
+ if (len < tcp_hdrlen || tcp_hdrlen < sizeof(struct tcphdr))
return -1;
if (info->mss == XT_TCPMSS_CLAMP_PMTU) {
@@ -152,6 +152,10 @@ tcpmss_mangle_packet(struct sk_buff *skb
if (len > tcp_hdrlen)
return 0;
+ /* tcph->doff has 4 bits, do not wrap it to 0 */
+ if (tcp_hdrlen >= 15 * 4)
+ return 0;
+
/*
* MSS Option not found ?! add it..
*/
Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are
queue-4.9/fix-an-intermittent-pr_emerg-warning-about-lo-becoming-free.patch
queue-4.9/netfilter-xt_tcpmss-add-more-sanity-tests-on-tcph-doff.patch
queue-4.9/ipv6-release-dst-on-error-in-ip6_dst_lookup_tail.patch
queue-4.9/igmp-acquire-pmc-lock-for-ip_mc_clear_src.patch