diff options
| author | Eric Dumazet <edumazet@google.com> | 2017-04-03 10:55:11 -0700 |
|---|---|---|
| committer | Sasha Levin <alexander.levin@verizon.com> | 2017-07-31 13:37:48 -0400 |
| commit | a7776b8815a90da464f045f7c24d9565ae9f1963 (patch) | |
| tree | c1d08146ba541bdc21371b55775a8ffa229850a9 /net | |
| parent | 2b1915e2ac70661e1ee08178df4e5b7f81b4b32d (diff) | |
netfilter: xt_TCPMSS: add more sanity tests on tcph->doff
[ Upstream commit 2638fd0f92d4397884fd991d8f4925cb3f081901 ]
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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
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 e762de5ee89b..6531d7039b11 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) { @@ -156,6 +156,10 @@ 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.. */ |