Re: [PATCH] x86/EFI: additional checks in efi_bgrt_init()

[Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>]

On Mon, Nov 05, 2012 at 06:43:46PM +0000, Matthew Garrett wrote:
> On Mon, Nov 05, 2012 at 10:37:52AM -0800, Josh Triplett wrote:
> > On Mon, Nov 05, 2012 at 03:26:41PM +0000, Jan Beulich wrote:
> > > Header length should be validated for all ACPI tables before accessing
> > > any non-header field.
> > > 
> > > The valid flags should also be check, as with it clear there's no point
> > > in trying to go through the rest of the code (and there's no guarantee
> > > that the other table contents are valid/consistent in that case).
> > > 
> > > Signed-off-by: Jan Beulich <jbeulich-IBi9RG/b67k@public.gmane.org>
> > 
> > The length check seems reasonable.  However, Matthew Garrett (already
> > CCed) previously suggested to me that this code should not check the
> > "valid" bit, and should instead present the information to userspace if
> > otherwise valid (such as having image_address != 0).  Matthew?
> 
> Yeah, my interpretation of the spec is that "valid" indicates whether or 
> not the contents represent what's currently on the screen, not whether 
> or not the contents can be interpreted for other reasons.

Given that, in the absence of a real BIOS that interprets the spec
differently than that, it sounds like we should drop the check for the
valid bit.

Jan, have you seen a real BIOS which disagrees with the above
interpretation?  If not, can you resubmit the patch with just the length
check?

- Josh Triplett