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From: Joerg Roedel <joro@8bytes.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Paul Menzel <pmenzel@molgen.mpg.de>,
	linux-mm@kvack.org, x86@kernel.org,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: x86/mm: Found insecure W+X mapping at address (ptrval)/0xc00a0000
Date: Thu, 4 Oct 2018 10:03:21 +0200	[thread overview]
Message-ID: <20181004080321.GA3630@8bytes.org> (raw)
In-Reply-To: <20181003212255.GB28361@zn.tnic>

On Wed, Oct 03, 2018 at 11:22:55PM +0200, Borislav Petkov wrote:
> On Fri, Sep 28, 2018 at 04:55:19PM +0200, Thomas Gleixner wrote:
> > Sorry for the delay and thanks for the data. A quick diff did not reveal
> > anything obvious. I'll have a closer look and we probably need more (other)
> > information to nail that down.

I also triggered this when working in the PTI-x32 code. It always
happens on a 32-bit PAE kernel for me.

Tracking it down I ended up in (iirc) arch/x86/mm/pageattr.c
	function static_protections():

		/*
		 * The BIOS area between 640k and 1Mb needs to be executable for
		 * PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
		 */
	#ifdef CONFIG_PCI_BIOS
		if (pcibios_enabled && within(pfn, BIOS_BEGIN >> PAGE_SHIFT, BIOS_END >> PAGE_SHIFT))
			pgprot_val(forbidden) |= _PAGE_NX;
	#endif

I think that is the reason we are seeing this in that configuration.


Regards,

	Joerg

  parent reply	other threads:[~2018-10-04  8:03 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-19  6:55 x86/mm: Found insecure W+X mapping at address (ptrval)/0xc00a0000 Paul Menzel
2018-09-19  8:09 ` Thomas Gleixner
2018-09-20  7:07   ` Paul Menzel
2018-09-20 22:51     ` Thomas Gleixner
2018-09-24 21:47       ` Paul Menzel
2018-09-28 14:55         ` Thomas Gleixner
2018-10-03 21:22           ` Borislav Petkov
2018-10-04  3:11             ` Paul Menzel
2018-10-04  7:48               ` Borislav Petkov
2018-10-04  8:03             ` Joerg Roedel [this message]
2018-10-04  8:14               ` Borislav Petkov
2018-10-04  8:40                 ` Paul Menzel
2018-10-04  8:49                   ` Borislav Petkov
2018-10-04  8:59                     ` Paul Menzel
2018-10-04 10:54                       ` Borislav Petkov
2018-10-04 11:00                         ` Paul Menzel
2018-10-04 11:12                           ` Borislav Petkov
2018-10-04  8:43                 ` Joerg Roedel
2018-10-04  8:48                   ` Borislav Petkov
2018-10-05  9:27               ` Thomas Gleixner
2018-10-05  9:39                 ` Paul Menzel
2018-10-08 19:37                   ` Thomas Gleixner
2018-10-08 20:08                     ` Bjorn Helgaas

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