Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-ID: <1533800010.5087.71.camel@gmx.de>
Subject: Re: [PATCH] x86, kdump: Fix efi=noruntime NULL pointer dereference
From:   Mike Galbraith <efault@gmx.de>
To:     Dave Young <dyoung@redhat.com>
Cc:     Baoquan He <bhe@redhat.com>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        lkml <linux-kernel@vger.kernel.org>, kexec@lists.infradead.org
Date:   Thu, 09 Aug 2018 09:33:30 +0200
In-Reply-To: <20180809042153.GA4377@dhcp-128-65.nay.redhat.com>
References: <1533737025.4936.3.camel@gmx.de>
         <20180809042153.GA4377@dhcp-128-65.nay.redhat.com>
Content-Type: text/plain; charset="ISO-8859-15"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, 2018-08-09 at 12:21 +0800, Dave Young wrote:
> Hi Mike,
> 
> Thanks for the patch!
> On 08/08/18 at 04:03pm, Mike Galbraith wrote:
> > When booting with efi=noruntime, we call efi_runtime_map_copy() while
> > loading the kdump kernel, and trip over a NULL efi.memmap.map.  Avoid
> > that and a useless allocation when the only mapping we can use (1:1)
> > is not available.
> 
> At first glance, efi_get_runtime_map_size should return 0 in case
> noruntime.

What efi does internally at unmap time is to leave everything except
efi.mmap.map untouched, setting it to NULL and turning off EFI_MEMMAP,
rendering efi.mmap.map accessors useless/unsafe without first checking
EFI_MEMMAP.

	-Mike