linux-kernel - Re: [PATCH] selftests: proc: Make sure wchan works when it exists

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]

Date:   Thu, 21 Oct 2021 17:39:38 -0700
From:   "Andy Lutomirski" <luto@...nel.org>
To:     "Kees Cook" <keescook@...omium.org>
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Mark Rutland" <mark.rutland@....com>,
        "Shuah Khan" <shuah@...nel.org>,
        "Alexey Dobriyan" <adobriyan@...il.com>,
        linux-kselftest@...r.kernel.org,
        "Josh Poimboeuf" <jpoimboe@...hat.com>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        "Alexey Gladkov" <gladkov.alexey@...il.com>,
        "Jann Horn" <jannh@...gle.com>,
        "Vito Caputo" <vcaputo@...garu.com>,
        "Ingo Molnar" <mingo@...hat.com>, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        "Steven Rostedt" <rostedt@...dmis.org>,
        "Ben Segall" <bsegall@...gle.com>, mgorman@...e.de,
        bristot@...hat.com,
        "Christian Brauner" <christian.brauner@...ntu.com>,
        amistry@...gle.com, Kenta.Tada@...y.com, legion@...nel.org,
        michael.weiss@...ec.fraunhofer.de,
        "Michal Hocko" <mhocko@...e.com>, deller@....de,
        "Qi Zheng" <zhengqi.arch@...edance.com>, me@...in.cc,
        tycho@...ho.pizza, "Thomas Gleixner" <tglx@...utronix.de>,
        "Borislav Petkov" <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
        "Jens Axboe" <axboe@...nel.dk>, metze@...ba.org,
        "Lai Jiangshan" <laijs@...ux.alibaba.com>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        ohoono.kwon@...sung.com, kaleshsingh@...gle.com,
        yifeifz2@...inois.edu, linux-arch@...r.kernel.org,
        vgupta@...nel.org, "Russell King (Oracle)" <linux@...linux.org.uk>,
        "Will Deacon" <will@...nel.org>, guoren@...nel.org,
        bcain@...eaurora.org, monstr@...str.eu, tsbogend@...ha.franken.de,
        nickhu@...estech.com, jonas@...thpole.se,
        "Michael Ellerman" <mpe@...erman.id.au>,
        "Paul Walmsley" <paul.walmsley@...ive.com>, hca@...ux.ibm.com,
        ysato@...rs.sourceforge.jp, davem@...emloft.net, chris@...kel.net,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] selftests: proc: Make sure wchan works when it exists



On Thu, Oct 21, 2021, at 1:12 PM, Kees Cook wrote:
> On Thu, Oct 21, 2021 at 01:03:33PM -0700, Andy Lutomirski wrote:
>> 
>> 
>> On Fri, Oct 8, 2021, at 4:55 PM, Kees Cook wrote:
>> > This makes sure that wchan contains a sensible symbol when a process is
>> > blocked. Specifically this calls the sleep() syscall, and expects the
>> > architecture to have called schedule() from a function that has "sleep"
>> > somewhere in its name. For example, on the architectures I tested
>> > (x86_64, arm64, arm, mips, and powerpc) this is "hrtimer_nanosleep":
>> 
>> Is this really better than admitting that the whole mechanism is nonsense and disabling it?
>> 
>> We could have a fixed string for each task state and call it a day.
>
> I consider this to be "future work". In earlier discussions it came up,
> but there wasn't an obvious clean cost-free way to do this, so instead
> we're just fixing the broken corner and keeping the mostly working rest
> of it while cleaning up the weird edges. :)

True, but we have the caveat that wchan is currently broken, so in some sense we have an easier time killing it now as compared to later.  But if we don't have a fully-fleshed-out idea for how to kill it, then I'm fine with waiting.

>
> -- 
> Kees Cook