Messages in this thread | | | Date | Mon, 03 Apr 2017 11:10:44 +0300 | From | Denys Fedoryshchenko <> | Subject | Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 |
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On 2017-04-02 20:26, Eric Dumazet wrote: > On Sun, 2017-04-02 at 10:14 -0700, Eric Dumazet wrote: > >> Could that be that netfilter does not abort earlier if TCP header is >> completely wrong ? >> > > Yes, I wonder if this patch would be better, unless we replicate the > th->doff sanity check in all netfilter modules dissecting TCP frames. > > diff --git a/net/netfilter/xt_tcpudp.c b/net/netfilter/xt_tcpudp.c > index > ade024c90f4f129a7c384e9e1cbfdb8ffe73065f..8cb4eadd5ba1c20e74bc27ee52a0bc36a5b26725 > 100644 > --- a/net/netfilter/xt_tcpudp.c > +++ b/net/netfilter/xt_tcpudp.c > @@ -103,11 +103,11 @@ static bool tcp_mt(const struct sk_buff *skb, > struct xt_action_param *par) > if (!NF_INVF(tcpinfo, XT_TCP_INV_FLAGS, > (((unsigned char *)th)[13] & tcpinfo->flg_mask) == > tcpinfo->flg_cmp)) > return false; > + if (th->doff * 4 < sizeof(_tcph)) { > + par->hotdrop = true; > + return false; > + } > if (tcpinfo->option) { > - if (th->doff * 4 < sizeof(_tcph)) { > - par->hotdrop = true; > - return false; > - } > if (!tcp_find_option(tcpinfo->option, skb, par->thoff, > th->doff*4 - sizeof(_tcph), > tcpinfo->invflags & XT_TCP_INV_OPTION, I modified patch a little as: if (th->doff * 4 < sizeof(_tcph)) { par->hotdrop = true; WARN_ON_ONCE(!tcpinfo->option); return false; }
And it did triggered WARN once at morning, and didn't hit KASAN. I will run for a while more, to see if it is ok, and then if stable, will try to enable SFQ again.
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