diff options
| author | Eric Dumazet | 2017-04-03 10:55:11 -0700 |
|---|---|---|
| committer | Pablo Neira Ayuso | 2017-04-08 22:24:19 +0200 |
| commit | 2638fd0f92d4397884fd991d8f4925cb3f081901 (patch) | |
| tree | f7c6cce4be9a84861a75ee58a2106a23cd79b91a /net | |
| parent | 0b9aefea860063bb39e36bd7fe6c7087fed0ba87 (diff) | |
netfilter: xt_TCPMSS: add more sanity tests on tcph->doff
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>
Diffstat (limited to 'net')
| -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 27241a767f17..c64aca611ac5 100644 --- 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.. */ |