From: Thomas Gleixner <tglx@linutronix.de>
To: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Baoquan He <bhe@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Ingo Molnar <mingo@kernel.org>, Kees Cook <keescook@chromium.org>,
thgarnie@google.com, caoj.fnst@cn.fujitsu.com,
izumi.taku@jp.fujitsu.com
Subject: Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
Date: Tue, 4 Jul 2017 17:46:35 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.20.1707041744510.9000@nanos> (raw)
In-Reply-To: <20170704153633.GA3149@codeblueprint.co.uk>
On Tue, 4 Jul 2017, Matt Fleming wrote:
> On Tue, 04 Jul, at 04:46:58PM, Thomas Gleixner wrote:
> > On Tue, 4 Jul 2017, Baoquan He wrote:
> >
> > > In fact I just referred to code in setup_arch(). Now I have a question,
> > > though CONFIG_EFI=y but efi firmware is not enabled,
> > > boot_params.efi_info.efi_loader_signature should be initilized to 0.
> > > Then below code is also problematic.
> > >
> > > #ifdef CONFIG_EFI
> > > if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
> > > EFI32_LOADER_SIGNATURE, 4)) {
> > > set_bit(EFI_BOOT, &efi.flags);
> > > } else if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
> > > EFI64_LOADER_SIGNATURE, 4)) {
> > > set_bit(EFI_BOOT, &efi.flags);
> > > set_bit(EFI_64BIT, &efi.flags);
> > > }
> > >
> > > if (efi_enabled(EFI_BOOT))
> > > efi_memblock_x86_reserve_range();
> > > #endif
> >
> > Indeed. Matt?
>
> It's possibly that I'm missing some context, but boot_params should be
> zero'd -- the x86 boot protocol requires that the entire data
> structure be zero'd on allocation.
>
> Have I missed something?
No. I misread the code. The strncmp() operates on
boot_params.efi_info.efi_loader_signature itself, so yes, all is fine.
It's just Baoquans copy and paste wreckage which is busted.
Thanks,
tglx
next prev parent reply other threads:[~2017-07-04 15:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-04 8:04 [PATCH v2 0/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Baoquan He
2017-07-04 8:04 ` [PATCH v2 1/2] x86/boot/KASLR: Adapt process_e820_entry for any type of memory entry Baoquan He
2017-07-05 22:06 ` Kees Cook
2017-07-06 1:21 ` Baoquan He
2017-07-04 8:04 ` [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Baoquan He
2017-07-04 14:00 ` Thomas Gleixner
2017-07-04 14:30 ` Baoquan He
2017-07-04 14:46 ` Thomas Gleixner
2017-07-04 15:36 ` Matt Fleming
2017-07-04 15:46 ` Thomas Gleixner [this message]
2017-07-04 23:16 ` Baoquan He
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