linux-kernel - Re: [PATCH v7u1 20/31] x86, kexec: replace ident_mapping_init and init_level4

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Message-ID: <CAE9FiQUZcbysdtmdnbnrciqaYqfbX8EkS_-FX_w2zvEe=w33QQ@mail.gmail.com>
Date:	Wed, 9 Jan 2013 17:26:18 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Borislav Petkov <bp@...en8.de>, Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kiszka <jan.kiszka@....de>,
	Jason Wessel <jason.wessel@...driver.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7u1 20/31] x86, kexec: replace ident_mapping_init and init_level4_page

On Sat, Jan 5, 2013 at 5:24 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Fri, Jan 04, 2013 at 02:04:05PM -0800, Yinghai Lu wrote:
>> On Fri, Jan 4, 2013 at 1:01 PM, Borislav Petkov <bp@...en8.de> wrote:
>> > On Thu, Jan 03, 2013 at 04:48:40PM -0800, Yinghai Lu wrote:
>> >>  static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
>> >>  {
>> >> +     struct x86_mapping_info info = {
>> >> +             .alloc_pgt_page = alloc_pgt_page,
>> >> +             .context        = image,
>> >> +             .pmd_flag       = __PAGE_KERNEL_LARGE_EXEC,
>> >> +     };
>> >
>> > This is leaving ->kernel_mapping uninitialized to contain a random,
>> > previous stack value. I don't think we want that.
>>
>> that should be initialized to false by default.
>
> So make it explicit. You can't possibly rely on what the stack contains
> when you allocate that struct there.

I should say:

that *is* initialized to false by default.

please check

http://stackoverflow.com/questions/10828294/c-and-c-partial-initialization-of-automatic-structure
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