linux-kernel - Re: [PATCH v10 2/5] sched: CGroup tagging interface for core scheduling

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: <YB0zSwrAozzRxhFV@hirez.programming.kicks-ass.net>
Date:   Fri, 5 Feb 2021 13:00:11 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Vineeth Pillai <viremana@...ux.microsoft.com>,
        Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, mingo@...nel.org,
        torvalds@...ux-foundation.org, fweisbec@...il.com,
        keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>, vineeth@...byteword.org,
        Chen Yu <yu.c.chen@...el.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Agata Gruza <agata.gruza@...el.com>,
        Antonio Gomez Iglesias <antonio.gomez.iglesias@...el.com>,
        graf@...zon.com, konrad.wilk@...cle.com, dfaggioli@...e.com,
        pjt@...gle.com, rostedt@...dmis.org, derkling@...gle.com,
        benbjiang@...cent.com,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        James.Bottomley@...senpartnership.com, OWeisse@...ch.edu,
        Dhaval Giani <dhaval.giani@...cle.com>,
        Junaid Shahid <junaids@...gle.com>, jsbarnes@...gle.com,
        chris.hyser@...cle.com, Ben Segall <bsegall@...gle.com>,
        Josh Don <joshdon@...gle.com>, Hao Luo <haoluo@...gle.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH v10 2/5] sched: CGroup tagging interface for core
 scheduling

On Fri, Jan 22, 2021 at 08:17:01PM -0500, Joel Fernandes (Google) wrote:
> +int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2)
> +{
> +	static DEFINE_MUTEX(sched_core_tasks_mutex);
> +	unsigned long cookie;
> +	int ret = -ENOMEM;
> +
> +	mutex_lock(&sched_core_tasks_mutex);
> +
> +	if (!t2) {
> +		if (t1->core_task_cookie) {
> +			sched_core_put_task_cookie(t1->core_task_cookie);
> +			sched_core_update_task_cookie(t1, 0);
> +			sched_core_put();
> +		}

So this seems to be the bit that implements _CLEAR. ISTR there were
security implications / considerations here.

When the machine is vulnerable to L1TF/MDS and the like, clearing the
cookie would gain privilege and should thus be subject to some checks,
but I can'd find anything.

At the very least that deserves a comment I'm thinking.