diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-04-03 10:55:11 -0700 |
|---|---|---|
| committer | Moyster <oysterized@gmail.com> | 2017-11-06 15:29:31 +0100 |
| commit | 86fdf06294d0cbdbb874c8702be242acfe199e93 (patch) | |
| tree | b4a5551197b217e396e44e00504a1e7a100c9542 | |
| parent | 329efc6a8f4ac3ad0ca2d3ac8424cda2a642ba51 (diff) | |
netfilter: xt_TCPMSS: add more sanity tests on tcph->doff
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@google.com>
Reported-by: Denys Fedoryshchenko <nuclearcat@nuclearcat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[wt: adjust context]
Signed-off-by: Willy Tarreau <w@1wt.eu>
| -rw-r--r-- | net/netfilter/xt_TCPMSS.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c index 7011c7164..c656269c4 100644 --- a/net/netfilter/xt_TCPMSS.c +++ b/net/netfilter/xt_TCPMSS.c @@ -68,7 +68,7 @@ tcpmss_mangle_packet(struct sk_buff *skb, tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); /* Header cannot be larger than the packet */ - if (tcplen < tcph->doff*4) + if (tcplen < tcph->doff*4 || tcph->doff*4 < sizeof(struct tcphdr)) return -1; if (info->mss == XT_TCPMSS_CLAMP_PMTU) { @@ -117,6 +117,10 @@ tcpmss_mangle_packet(struct sk_buff *skb, if (tcplen > tcph->doff*4) return 0; + /* tcph->doff has 4 bits, do not wrap it to 0 */ + if (tcph->doff >= 15) + return 0; + /* * MSS Option not found ?! add it.. */ |