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

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Message-ID: <20130105132447.GD4297@x1.alien8.de>
Date:	Sat, 5 Jan 2013 14:24:47 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	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 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.

-- 
Regards/Gruss,
Boris.
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