netdev - Re: [PATCH net] bpf: disable broken write protection on i386

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <58C075BC.8050004@iogearbox.net>
Date:   Wed, 08 Mar 2017 22:21:00 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Kees Cook <keescook@...omium.org>
CC:     "David S. Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Laura Abbott <labbott@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH net] bpf: disable broken write protection on i386

On 03/08/2017 07:40 PM, Kees Cook wrote:
> On Mon, Mar 6, 2017 at 10:11 AM, Kees Cook <keescook@...omium.org> wrote:
>> On Fri, Mar 3, 2017 at 7:23 PM, Daniel Borkmann <daniel@...earbox.net> wrote:
>>> Latter shows that memory protecting the kernel seems not working either
>>> on i386 (!). Test suite output:
>>>
>>>    [...]
>>>    [   12.692836] Write protecting the kernel text: 13416k
>>>    [   12.693309] Write protecting the kernel read-only data: 5292k
>>>    [   12.693802] rodata_test: test data was not read only
>>>    [...]
>>>
>>> Work-around to not enable ARCH_HAS_SET_MEMORY for i386 is not optimal
>>> as it doesn't fix the issue in presumably broken set_memory_*(), but
>>> it at least avoids people avoid having to deal with random corruptions
>>> that are hard to track down for the time being until a real fix can
>>> be found.
>>
>> Wow. Uhm, so, something must be _really_ broken. i386 should have no
>> problem with using the set_memory_*() functions. The fact that
>> DEBUG_RODATA_TEST failed is also pretty crazy, but may be unrelated
>> (that test was just refactored too).
>
> I'm not able to reproduce this. I built Linus's tree and rodata_test
> passes for me on i386. I tried the .config from Fengguang (with
> RODATA_TEST=y added), but it still passes for me:
> https://lkml.org/lkml/2017/3/1/344
>
> I wonder if something change changed already in the tree? Can you
> still reproduce this?

I'll answer in a bit an will move the discussion over to the other
thread on the same topic ("[net/bpf] 3051bf36c2 BUG: unable to handle
kernel paging request at 0000a7cf" [1]) with you, Laura and Dave in
Cc as well.

   [1] https://lkml.org/lkml/2017/3/8/620