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Groups > linux.kernel > #1614720
| From | Eric Dumazet <eric.dumazet@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 |
| Date | 2017-04-02 14:00 +0200 |
| Message-ID | <trMkN-8nM-3@gated-at.bofh.it> (permalink) |
| References | <trIqS-5Yh-7@gated-at.bofh.it> <trLRL-8ck-9@gated-at.bofh.it> <trMb7-8kH-19@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Sun, 2017-04-02 at 13:45 +0200, Florian Westphal wrote:
> Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > - for (i = sizeof(struct tcphdr); i <= tcp_hdrlen - TCPOLEN_MSS; i += optlen(opt, i)) {
> > + for (i = sizeof(struct tcphdr); i < tcp_hdrlen - TCPOLEN_MSS; i += optlen(opt, i)) {
> > if (opt[i] == TCPOPT_MSS && opt[i+1] == TCPOLEN_MSS) {
> > u_int16_t oldmss;
>
> maybe I am low on caffeeine but this looks fine, for tcp header with
> only tcpmss this boils down to "20 <= 24 - 4" so we acccess offsets 20-23 which seems ok.
I am definitely low on caffeine ;)
An issue in this function is that we might add the missing MSS option,
without checking that TCP options are already full.
But this should not cause a KASAN splat, only some malformed TCP packet
(tcph->doff would wrap)
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KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Denys Fedoryshchenko <nuclearcat@nuclearcat.com> - 2017-04-02 09:50 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-02 13:30 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Florian Westphal <fw@strlen.de> - 2017-04-02 13:50 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Denys Fedoryshchenko <nuclearcat@nuclearcat.com> - 2017-04-02 14:00 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-02 14:00 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-02 14:30 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Denys Fedoryshchenko <nuclearcat@nuclearcat.com> - 2017-04-02 14:30 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-02 14:40 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Denys Fedoryshchenko <nuclearcat@nuclearcat.com> - 2017-04-02 19:00 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-02 19:20 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-02 19:30 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Denys Fedoryshchenko <nuclearcat@nuclearcat.com> - 2017-04-03 10:20 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-03 14:10 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Denys Fedoryshchenko <nuclearcat@nuclearcat.com> - 2017-04-03 14:20 +0200
Re: KASAN, xt_TCPMSS finally found nasty use-after-free bug? 4.10.8 Eric Dumazet <eric.dumazet@gmail.com> - 2017-04-03 14:30 +0200
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