On 06/02/16 at 10:24am, Matt Fleming wrote:
> On Sun, 29 May, at 06:09:01AM, Môshe van der Sterre wrote:
> > ---
> > arch/x86/platform/efi/efi-bgrt.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/arch/x86/platform/efi/efi-bgrt.c b/arch/x86/platform/efi/efi-bgrt.c
> > index 6a2f569..a7fdb61 100644
> > --- a/arch/x86/platform/efi/efi-bgrt.c
> > +++ b/arch/x86/platform/efi/efi-bgrt.c
> > @@ -19,6 +19,8 @@
> > #include <linux/efi.h>
> > #include <linux/efi-bgrt.h>
> >
> > +#include "../../mm/physaddr.h"
> > +
> > struct acpi_table_bgrt *bgrt_tab;
> > void *__initdata bgrt_image;
> > size_t __initdata bgrt_image_size;
> > @@ -67,6 +69,11 @@ void __init efi_bgrt_init(void)
> > return;
> > }
> >
> > + if (!phys_addr_valid(bgrt_tab->image_address)) {
> > + pr_notice("Ignoring BGRT: image address is bogus\n");
> > + return;
> > + }
> > +
> > image = memremap(bgrt_tab->image_address, sizeof(bmp_header), MEMREMAP_WB);
> > if (!image) {
> > pr_notice("Ignoring BGRT: failed to map image header memory\n");
> > --
> > 2.4.3
> >
>
> If this does indeed fix Andy's immediate issue (and it looks like
> it would) I'm happy to apply this as an interim solution.
>
> Once we have a persistent EFI memmap available at runtime on x86 we
> should attempt to see whether the physical address in ->image_address
> is covered by some region in that table. The persistent EFI memmap
> patches should be posted in the coming weeks.
I may missed the background but I worry about who knows if it is meant
to be used for BGRT image. Some vendors could respect the BGRT valid
bit and just leave the address as a random address. And the random
address could be a valid physical address though. It is possible to
leak memory infomation.
Could we reconsider about below commit? It may be a Windows 10 bug?
commit 66dbe99cfe30e113d2e571e68b9b6a1a8985a157
Author: Môshe van der Sterre <me@xxxxxxxx>
Date: Mon Feb 1 22:07:03 2016 +0000
x86/efi/bgrt: Don't ignore the BGRT if the 'valid' bit is 0
Thanks
Dave
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