linux-kernel - Re: [Patch v2 4/4] x86/speculation: Add prctl to control indirect branch speculation per process

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Message-ID: <5a558b4e-e241-2ab8-3653-b25dc014b78d@linux.intel.com>
Date:   Fri, 5 Oct 2018 11:12:23 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Subject: Re: [Patch v2 4/4] x86/speculation: Add prctl to control indirect
 branch speculation per process

On 10/02/2018 10:58 AM, Thomas Gleixner wrote:
> On Tue, 25 Sep 2018, Tim Chen wrote:
>>  
>> +void arch_set_dumpable(struct task_struct *tsk, struct mm_struct *mm, int value)
>> +{
>> +	if (!static_branch_unlikely(&spectre_v2_app_lite))
>> +		return;
>> +	if (!static_cpu_has(X86_FEATURE_STIBP))
>> +		return;
>> +
>> +	if ((unsigned) value != SUID_DUMP_USER) {
> 
> First of all we use unsigned int and not unsigned, Aside of that why is the
> argument not unsigned int right away?


The original set_dumpable passes suid_dumpable, which was
exposed via /proc/sys/fs/suid_dumpable and defined as int.
It will make sense to define suid_dumpable as an unsigned int instead.

Would you like me to redefine suid_dumpable as unsigned int
in sysctl.c in the patch revision as a separate clean up patch?

Thanks.

Tim