Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

From	Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Date	2015-11-05 15:00 +0100
Message-ID	<qrtf4-7pc-3@gated-at.bofh.it> (permalink)
References	(2 earlier) <qrbi9-47z-15@gated-at.bofh.it> <qrbi9-47z-13@gated-at.bofh.it> <qrcxA-59d-9@gated-at.bofh.it> <qrfvr-72q-1@gated-at.bofh.it> <qroS5-4FF-3@gated-at.bofh.it>
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On 11/05/2015 04:13 AM, Sander Eikelenboom wrote:
>
> It makes "cat /sys/kernel/debug/kernel_page_tables" work and
> prevents a kernel with CONFIG_DEBUG_WX=y from crashing at boot.

Great. Our nightly runs also failed spectacularly due to this bug.

>
> It now does give a warning about an insecure W+X mapping, so 
> CONFIG_DEBUG_WX=y
> seems to be working. No idea how to interpret it though (and if it's a 
> legit
> warning).
>
> -- 
> Sander
>
> [   19.034706] Freeing unused kernel memory: 1104K (ffffffff822fc000 - 
> ffffffff82410000)
> [   19.041339] Write protecting the kernel read-only data: 18432k
> [   19.052596] Freeing unused kernel memory: 1144K (ffff880001ae2000 - 
> ffff880001c00000)
> [   19.060285] Freeing unused kernel memory: 1560K (ffff88000207a000 - 
> ffff880002200000)
> [   19.067079] ------------[ cut here ]------------
> [   19.073931] WARNING: CPU: 5 PID: 1 at 
> arch/x86/mm/dump_pagetables.c:225 note_page+0x619/0x7e0()

Yes, this apparently is a known issue: https://lkml.org/lkml/2015/11/4/476

-boris


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Thread

Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-04 13:10 +0100
  Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled:  RIP: ptdump_walk_pgd_level_core Stephen Smalley <sds@tycho.nsa.gov> - 2015-11-04 17:00 +0100
    Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled:  RIP: ptdump_walk_pgd_level_core Ingo Molnar <mingo@kernel.org> - 2015-11-04 19:10 +0100
      Re: Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-04 19:20 +0100
    Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled:  RIP: ptdump_walk_pgd_level_core Stephen Smalley <sds@tycho.nsa.gov> - 2015-11-04 19:50 +0100
      Re: Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-04 21:10 +0100
        Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-05 00:20 +0100
          Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-05 10:20 +0100
            Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-05 15:00 +0100
              Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-05 15:10 +0100
      Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-04 21:20 +0100

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