linux-kernel - Re: [PATCH 4.11 049/150] efi/bgrt: Skip efi_bgrt

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Message-ID: <20170615071743.GC25693@kroah.com>
Date:   Thu, 15 Jun 2017 09:17:43 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Maniaxx <tripleshiftone@...il.com>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Sabrina Dubroca <sd@...asysnail.net>,
        Dave Young <dyoung@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-efi@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 4.11 049/150] efi/bgrt: Skip efi_bgrt_init() in case of
 non-EFI boot

On Thu, Jun 15, 2017 at 01:34:38AM +0200, Maniaxx wrote:
> On 12.06.2017 at 17:24 wrote Greg Kroah-Hartman:
> > 4.11-stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Dave Young <dyoung@...hat.com>
> > 
> > commit 7425826f4f7ac60f2538b06a7f0a5d1006405159 upstream.
> > 
> > Sabrina Dubroca reported an early panic:
> > 
> >   BUG: unable to handle kernel paging request at ffffffffff240001
> >   IP: efi_bgrt_init+0xdc/0x134
> > 
> >   [...]
> > 
> >   ---[ end Kernel panic - not syncing: Attempted to kill the idle task!
> > 
> > ... which was introduced by:
> > 
> >   7b0a911478c7 ("efi/x86: Move the EFI BGRT init code to early init code")
> > 
> > The cause is that on this machine the firmware provides the EFI ACPI BGRT
> > table even on legacy non-EFI bootups - which table should be EFI only.
> > 
> > The garbage BGRT data causes the efi_bgrt_init() panic.
> > 
> > Add a check to skip efi_bgrt_init() in case non-EFI bootup to work around
> > this firmware bug.
> > 
> > Tested-by: Sabrina Dubroca <sd@...asysnail.net>
> > Signed-off-by: Dave Young <dyoung@...hat.com>
> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
> > Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: linux-efi@...r.kernel.org
> > Fixes: 7b0a911478c7 ("efi/x86: Move the EFI BGRT init code to early init code")
> > Link: http://lkml.kernel.org/r/20170526113652.21339-6-matt@codeblueprint.co.uk
> > [ Rewrote the changelog to be more readable. ]
> > Signed-off-by: Ingo Molnar <mingo@...nel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > 
> > ---
> >  arch/x86/platform/efi/efi-bgrt.c |    3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > --- a/arch/x86/platform/efi/efi-bgrt.c
> > +++ b/arch/x86/platform/efi/efi-bgrt.c
> > @@ -36,6 +36,9 @@ void __init efi_bgrt_init(struct acpi_ta
> >  	if (acpi_disabled)
> >  		return;
> >  
> > +	if (!efi_enabled(EFI_BOOT))
> > +		return;
> > +
> >  	if (table->length < sizeof(bgrt_tab)) {
> >  		pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
> >  		       table->length, sizeof(bgrt_tab));
> > 
> > 
> > 
> 
> The patch is ok but it only fixes BIOS systems.
> To fix the regression above (commit 7b0a911478c7) for EFI systems 
> it needs this patch as well:
> commit 792ef14df5c585c19b2831673a077504a09e5203 master
> (efi: Fix boot panic because of invalid BGRT image address)

Thanks for letting me know, now queued up.

greg k-h