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

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Message-Id: <f4b83c21-4e73-45b6-ae3a-17659be512c0@www.fastmail.com>
Date:   Thu, 21 Oct 2021 13:03:33 -0700
From:   "Andy Lutomirski" <luto@...nel.org>
To:     "Kees Cook" <keescook@...omium.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc:     "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 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.