linux-kernel - Re: [PATCH RFC V2 12/17] memremap: Add zone device access protection

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: <20200718055103.GU3008823@iweiny-DESK2.sc.intel.com>
Date:   Fri, 17 Jul 2020 22:51:03 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Fenghua Yu <fenghua.yu@...el.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH RFC V2 12/17] memremap: Add zone device access protection

On Fri, Jul 17, 2020 at 11:17:18AM +0200, Peter Zijlstra wrote:
> On Fri, Jul 17, 2020 at 12:20:51AM -0700, ira.weiny@...el.com wrote:
> > +void dev_access_disable(void)
> > +{
> > +	unsigned long flags;
> > +
> > +	if (!static_branch_unlikely(&dev_protection_static_key))
> > +		return;
> > +
> > +	local_irq_save(flags);
> > +	current->dev_page_access_ref--;
> > +	if (current->dev_page_access_ref == 0)
> 
> 	if (!--current->dev_page_access_ref)

It's not my style but I'm ok with it.

> 
> > +		pks_update_protection(dev_page_pkey, PKEY_DISABLE_ACCESS);
> > +	local_irq_restore(flags);
> > +}
> > +EXPORT_SYMBOL_GPL(dev_access_disable);
> > +
> > +void dev_access_enable(void)
> > +{
> > +	unsigned long flags;
> > +
> > +	if (!static_branch_unlikely(&dev_protection_static_key))
> > +		return;
> > +
> > +	local_irq_save(flags);
> > +	/* 0 clears the PKEY_DISABLE_ACCESS bit, allowing access */
> > +	if (current->dev_page_access_ref == 0)
> > +		pks_update_protection(dev_page_pkey, 0);
> > +	current->dev_page_access_ref++;
> 
> 	if (!current->dev_page_access_ref++)

Sure.

> 
> > +	local_irq_restore(flags);
> > +}
> > +EXPORT_SYMBOL_GPL(dev_access_enable);
> 
> 
> Also, you probably want something like:
> 
> static __always_inline devm_access_disable(void)

Yes that is better.

However, again Dan and I agree devm is not the right prefix here.

I've updated.

Thanks!
Ira

> {
> 	if (static_branch_unlikely(&dev_protection_static_key))
> 		__devm_access_disable();
> }
> 
> static __always_inline devm_access_enable(void)
> {
> 	if (static_branch_unlikely(&dev_protection_static_key))
> 		__devm_access_enable();
> }