linux-kernel - Re: [PATCH 3/5] efi arm64: do not enter virtual mode in case booting with efi=noruntime or noefi

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Message-ID: <20140812104627.GI29013@arm.com>
Date:	Tue, 12 Aug 2014 11:46:27 +0100
From:	Will Deacon <will.deacon@....com>
To:	Dave Young <dyoung@...hat.com>
Cc:	Matt Fleming <matt.fleming@...el.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	"msalter@...hat.com" <msalter@...hat.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"rtc-linux@...glegroups.com" <rtc-linux@...glegroups.com>
Subject: Re: [PATCH 3/5] efi arm64: do not enter virtual mode in case booting
 with efi=noruntime or noefi

On Tue, Aug 12, 2014 at 07:10:20AM +0100, Dave Young wrote:
> In case efi runtime disabled via noefi kernel cmdline arm64_enter_virtual_mode
> should error out.
> 
> At the same time move early_memunmap(memmap.map, mapsize) to the beginning of
> the function or it will leak early mem.
> 
> Signed-off-by: Dave Young <dyoung@...hat.com>
> ---
>  arch/arm64/kernel/efi.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index e72f310..324cdd1 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -386,7 +386,10 @@ static int __init arm64_enter_virtual_mode(void)
>  	int count = 0;
>  	unsigned long flags;
>  
> -	if (!efi_enabled(EFI_BOOT)) {
> +	mapsize = memmap.map_end - memmap.map;
> +	early_memunmap(memmap.map, mapsize);
> +
> +	if (!efi_enabled(EFI_BOOT) || efi_runtime_disabled()) {

Hmm, is this right? We only set EFI_BOOT if we find EFI parameters in the
DT (see efi_init -> uefi_init), so you run the risk of unmapping something
we never mapped here.

Furthermore, there seems to be a leak in uefi_init anyway, as we return
-EINVAL if the signature of the EFI table doesn't match without unmapping it
first.

Will
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