linux-kernel - Re: [GIT PULL] x86 fixes for 3.9

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Date:	Fri, 26 Apr 2013 09:29:19 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Matthew Garrett <matthew.garrett@...ula.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bp@...e.de>, "H. Peter Anvin" <hpa@...or.com>,
	Ingo Molnar <mingo@...e.hu>, Josh Boyer <jwboyer@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Matt Fleming <matt.fleming@...el.com>,
	Paul Bolle <pebolle@...cali.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [GIT PULL] x86 fixes for 3.9


* Matthew Garrett <matthew.garrett@...ula.com> wrote:

> On Thu, 2013-04-25 at 15:20 -0700, Linus Torvalds wrote:
> > On Thu, Apr 25, 2013 at 2:44 PM, H. Peter Anvin <hpa@...ux.intel.com> wrote:
> > >
> > > -       if (!sys_table->runtime->query_variable_info)
> > > +       if (sys_table->runtime->hdr.revision < EFI_2_00_SYSTEM_TABLE_REVISION)
> > >                 return EFI_UNSUPPORTED;
> > 
> > Is a EFI 2.00 system table *guaranteed* to have that
> > "query_variable_info" function? The above adds the version check, but
> > removes the check for a NULL pointer.
> 
> As far as the spec's concerned, yes. As far as reality's concerned - if
> anything doesn't provide it, we're already crashing when
> efi_virt_query_variable_info() gets called. Nobody's complained so far.

I'm worried about the fragility of this code - this is firmware code ...

I think firmware code should be fundamentally paranoid and robust, and in 
this case treat all EFI-provided data as hostile and do a much sanity 
checking of it as possible - and provide an actionable error message if 
the checks fail, not just 'crash'.

Even if no-one complained, yet.

Thanks,

	Ingo
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