From: Florian Westphal <fw@strlen.de>
To: Maxim Mikityanskiy <maximmi@nvidia.com>
Cc: "Florian Westphal" <fw@strlen.de>,
"Mat Martineau" <mathew.j.martineau@linux.intel.com>,
"Matthieu Baerts" <matthieu.baerts@tessares.net>,
"Jakub Kicinski" <kuba@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
"Pablo Neira Ayuso" <pablo@netfilter.org>,
"Jozsef Kadlecsik" <kadlec@netfilter.org>,
"Toke Høiland-Jørgensen" <toke@toke.dk>,
"Jamal Hadi Salim" <jhs@mojatatu.com>,
"Cong Wang" <xiyou.wangcong@gmail.com>,
"Jiri Pirko" <jiri@resnulli.us>,
"Patrick McHardy" <kaber@trash.net>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
"Paolo Abeni" <pabeni@redhat.com>,
"Christoph Paasch" <cpaasch@apple.com>,
"Peter Krystad" <peter.krystad@linux.intel.com>,
"Young Xiao" <92siuyang@gmail.com>,
netdev@vger.kernel.org
Subject: Re: [PATCH net 1/3] netfilter: synproxy: Fix out of bounds when parsing TCP options
Date: Thu, 10 Jun 2021 10:56:07 +0200 [thread overview]
Message-ID: <20210610085607.GN20020@breakpoint.cc> (raw)
In-Reply-To: <4ec99ea3-6ab1-eee4-be60-992cf2f9cd45@nvidia.com>
Maxim Mikityanskiy <maximmi@nvidia.com> wrote:
> On 2021-06-09 17:51, Florian Westphal wrote:
> > Maxim Mikityanskiy <maximmi@nvidia.com> wrote:
> > > The TCP option parser in synproxy (synproxy_parse_options) could read
> > > one byte out of bounds. When the length is 1, the execution flow gets
> > > into the loop, reads one byte of the opcode, and if the opcode is
> > > neither TCPOPT_EOL nor TCPOPT_NOP, it reads one more byte, which exceeds
> > > the length of 1.
> > >
> > > This fix is inspired by commit 9609dad263f8 ("ipv4: tcp_input: fix stack
> > > out of bounds when parsing TCP options.").
> > >
> > > Cc: Young Xiao <92siuyang@gmail.com>
> > > Fixes: 48b1de4c110a ("netfilter: add SYNPROXY core/target")
> > > Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
> > > ---
> > > net/netfilter/nf_synproxy_core.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
> > > index b100c04a0e43..621eb5ef9727 100644
> > > --- a/net/netfilter/nf_synproxy_core.c
> > > +++ b/net/netfilter/nf_synproxy_core.c
> > > @@ -47,6 +47,8 @@ synproxy_parse_options(const struct sk_buff *skb, unsigned int doff,
> > > length--;
> > > continue;
> > > default:
> > > + if (length < 2)
> > > + return true;
> >
> > Would you mind a v2 that also rejects bogus th->doff value when
> > computing the length?
>
> Could you elaborate? The length is a signed int calculated as `(th->doff *
> 4) - sizeof(*th)`. Invalid doff values (0..4) lead to negative length, so we
> never enter the loop. Or are you concerned of passing a negative length to
> skb_header_pointer?
Yes, negative length to skb_header_pointer. For other usage (mptcp for
example) tcp stack validated th->doff already, but thats not the case for synproxy.
next prev parent reply other threads:[~2021-06-10 8:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-09 14:22 [PATCH net 0/3] Fix out of bounds when parsing TCP options Maxim Mikityanskiy
2021-06-09 14:22 ` [PATCH net 1/3] netfilter: synproxy: " Maxim Mikityanskiy
2021-06-09 14:51 ` Florian Westphal
2021-06-10 7:05 ` Maxim Mikityanskiy
2021-06-10 8:56 ` Florian Westphal [this message]
2021-06-09 14:22 ` [PATCH net 2/3] mptcp: " Maxim Mikityanskiy
2021-06-10 0:07 ` Mat Martineau
2021-06-09 14:22 ` [PATCH net 3/3] sch_cake: " Maxim Mikityanskiy
2021-06-09 21:51 ` Toke Høiland-Jørgensen
2021-06-10 11:19 ` Maxim Mikityanskiy
2021-06-10 14:33 ` Toke Høiland-Jørgensen
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