linux-kernel - Re: [RFC PATCH 0/2] improve vmalloc allocation

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

Message-ID: <20181023193044.GA139403@joelaf.mtv.corp.google.com>
Date:   Tue, 23 Oct 2018 12:30:44 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Shuah Khan <shuah@...nel.org>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>,
        maco@...roid.com
Subject: Re: [RFC PATCH 0/2] improve vmalloc allocation

On Tue, Oct 23, 2018 at 11:13:36AM -0600, Shuah Khan wrote:
> On 10/23/2018 11:05 AM, Michal Hocko wrote:
> > On Tue 23-10-18 08:26:40, Matthew Wilcox wrote:
> >> On Tue, Oct 23, 2018 at 09:02:56AM -0600, Shuah Khan wrote:
> > [...]
> >>> The way it can be handled is by adding a test module under lib. test_kmod,
> >>> test_sysctl, test_user_copy etc.
> >>
> >> The problem is that said module can only invoke functions which are
> >> exported using EXPORT_SYMBOL.  And there's a cost to exporting them,
> >> which I don't think we're willing to pay, purely to get test coverage.
> > 
> > Yes, I think we do not want to export internal functionality which might
> > be still interesting for the testing coverage. Maybe we want something
> > like EXPORT_SYMBOL_KSELFTEST which would allow to link within the
> > kselftest machinery but it wouldn't allow the same for general modules
> > and will not give any API promisses.
> > 
> 
> I like this proposal. I think we will open up lot of test opportunities with
> this approach.
> 
> Maybe we can use this stress test as a pilot and see where it takes us.

I am a bit worried that such an EXPORT_SYMBOL_KSELFTEST mechanism can be abused by
out-of-tree module writers to call internal functionality.

How would you prevent that?

thanks,

 - Joel