linux-kernel - Re: [PATCH] efi/libstub/arm64: Report meaningful relocation errors

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Message-ID: <20190906104419.cyewsrnwcks7cbny@willie-the-truck>
Date:   Fri, 6 Sep 2019 11:44:20 +0100
From:   Will Deacon <will@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] efi/libstub/arm64: Report meaningful relocation errors

On Wed, Sep 04, 2019 at 01:38:04PM -0700, Kees Cook wrote:
> On Wed, Sep 04, 2019 at 11:38:03AM +0100, Will Deacon wrote:
> > On Wed, Aug 14, 2019 at 01:55:50PM -0700, Kees Cook wrote:
> > > diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
> > > index 1550d244e996..24022f956e01 100644
> > > --- a/drivers/firmware/efi/libstub/arm64-stub.c
> > > +++ b/drivers/firmware/efi/libstub/arm64-stub.c
> > > @@ -111,6 +111,8 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table_arg,
> > >  		status = efi_random_alloc(sys_table_arg, *reserve_size,
> > >  					  MIN_KIMG_ALIGN, reserve_addr,
> > >  					  (u32)phys_seed);
> > > +		if (status != EFI_SUCCESS)
> > > +			pr_efi_err(sys_table_arg, "KASLR allocate_pages() failed\n");
> > >  
> > >  		*image_addr = *reserve_addr + offset;
> > >  	} else {
> > > @@ -135,6 +137,8 @@ efi_status_t handle_kernel_image(efi_system_table_t *sys_table_arg,
> > >  					EFI_LOADER_DATA,
> > >  					*reserve_size / EFI_PAGE_SIZE,
> > >  					(efi_physical_addr_t *)reserve_addr);
> > > +		if (status != EFI_SUCCESS)
> > > +			pr_efi_err(sys_table_arg, "regular allocate_pages() failed\n");
> > >  	}
> > 
> > Not sure I see the need to distinsuish the 'KASLR' case from the 'regular'
> > case -- only one should run, right?  That also didn't seem to be part of
> > the use-case in the commit, unless I'm missing something.
> 
> I just did that to help with differentiating the cases. Maybe something
> was special about KASLR picking the wrong location that triggered the
> failure, etc.
> 
> > Maybe combine the prints as per the diff below?
> 
> That could work. If you're against the KASLR vs regular thing, I can
> respin the patch?

Happy to Ack it with that change, although I suppose it's ultimately up
to Ard :)

Will