linux-kernel - Re: [PATCH v2 2/3] x86/speculation: Apply IBPB more strictly to avoid cross-process spectre v2 leak

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: <nycvar.YFH.7.76.1809031555530.25787@cbobk.fhfr.pm>
Date:   Mon, 3 Sep 2018 15:57:51 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Oleg Nesterov <oleg@...hat.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH v2 2/3] x86/speculation: Apply IBPB more strictly to
 avoid cross-process spectre v2 leak

On Mon, 3 Sep 2018, Peter Zijlstra wrote:

> >  		if (tsk && tsk->mm &&
> >  		    tsk->mm->context.ctx_id != last_ctx_id &&
> > -		    get_dumpable(tsk->mm) != SUID_DUMP_USER)
> > +		    ___ptrace_may_access(tsk, current, PTRACE_MODE_IBPB))
> >  			indirect_branch_prediction_barrier();
> 
> So the question posed here is: can @next ptrace @prev?
> 
> Which confuses me greatly; it is @prev doing the BTB poisoning for
> @next, so we want to know if @prev can ptrace @next, no?

Good catch, it's the other way around, thanks.

I'll wait for more review and send eventually v3 properly threaded (sorry 
for that as well ... not the best monday I've had today).

-- 
Jiri Kosina
SUSE Labs