linux-kernel - 4.4-rc5: ugly warn on: 5 W+X pages found

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Date:	Mon, 14 Dec 2015 09:04:03 +0100
From:	Pavel Machek <pavel@....cz>
To:	kernel list <linux-kernel@...r.kernel.org>, sds@...ho.nsa.gov,
	luto@...capital.net, arjan@...ux.intel.com, bp@...en8.de,
	brgerst@...il.com, dvlasenk@...hat.com, hpa@...or.com,
	torvalds@...ux-foundation.org, efault@....de, peterz@...radead.org,
	tglx@...utronix.de
Subject: 4.4-rc5: ugly warn on: 5 W+X pages found

Hi!

> Kernel complains:

And now, we are at -rc5, and kernel still complains...

...with a back trace, which is clearly completely useless, and just
there to make it scary and make people report.

Problem is... noone cares for the reports. (-rc0 version below).

Can we get rid of that WARN_ON? If you do care about reports, please
add email address those can be reported to. If you don't... just drop
it.

Hardware is thinkpad x60.

								Pavel

[    3.267542] NX-protecting the kernel data: 5764k
[    3.278325] ------------[ cut here ]------------
[    3.282060] WARNING: CPU: 1 PID: 1 at
arch/x86/mm/dump_pagetables.c:225 note_page+0x5ec/0x790()
[    3.285993] x86/mm: Found insecure W+X mapping at address
ffe69000/0xffe69000
[    3.289991] Modules linked in:
[    3.293995] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.4.0-rc5+
#132
[    3.298178] Hardware name: LENOVO 17097HU/17097HU, BIOS 7BETD8WW
(2.19 ) 03/31/2011
[    3.304343]  00000001 00000000 f5cffeac c42ba698 f5cffed8 f5cffec8
c404059b 000000e1
[    3.308840]  c403cb9c f5cfff50 00000163 00000000 f5cffee0 c40405f6
00000009 f5cffed8
[    3.313419]  c4d3347c f5cffef4 f5cfff1c c403cb9c c4d2c08c 000000e1
c4d3347c ffe69000
[    3.317935] Call Trace:
[    3.322395]  [<c42ba698>] dump_stack+0x41/0x59
[    3.326787]  [<c404059b>] warn_slowpath_common+0x6b/0xa0
[    3.331171]  [<c403cb9c>] ? note_page+0x5ec/0x790
[    3.335522]  [<c40405f6>] warn_slowpath_fmt+0x26/0x30
[    3.339839]  [<c403cb9c>] note_page+0x5ec/0x790
[    3.344154]  [<c403ce9f>] ptdump_walk_pgd_level_core+0x15f/0x240
[    3.348440]  [<c403cfa1>] ptdump_walk_pgd_level_checkwx+0x11/0x20
[    3.352611]  [<c4034fdd>] mark_rodata_ro+0xcd/0xf0
[    3.356677]  [<c4a55c97>] kernel_init+0x17/0xc0
[    3.360702]  [<c4a5c409>] ret_from_kernel_thread+0x21/0x38
[    3.364739]  [<c4a55c80>] ? rest_init+0xa0/0xa0
[    3.368709] ---[ end trace 7121849c40f4a5ba ]---
[    3.372716] x86/mm: Checked W+X mappings: FAILED, 5 W+X pages
found.


> [    5.256044] ------------[ cut here ]------------
> [    5.259267] WARNING: CPU: 0 PID: 1 at
> arch/x86/mm/dump_pagetables.c:225 note_page+0x5ec/0x790()
> [    5.262668] x86/mm: Found insecure W+X mapping at address
> ffe69000/0xffe69000
> [    5.267109] Modules linked in:
> [    5.271403] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.3.0+ #122
> [    5.275679] Hardware name: LENOVO 17097HU/17097HU, BIOS 7BETD8WW
> (2.19 ) 03/31/2011
> [    5.279957]  00000000 00000000 f5cffeac c42b9f18 f5cffed8 f5cffec8
> c404062b 000000e1
> [    5.284387]  c403ca9c f5cfff50 00000163 00000000 f5cffee0 c4040686
> 00000009 f5cffed8
> [    5.288815]  c4d268ac f5cffef4 f5cfff1c c403ca9c c4d1f494 000000e1
> c4d268ac ffe69000
> [    5.293314] Call Trace:
> [    5.297602]  [<c42b9f18>] dump_stack+0x41/0x59
> [    5.301864]  [<c404062b>] warn_slowpath_common+0x6b/0xa0
> [    5.306054]  [<c403ca9c>] ? note_page+0x5ec/0x790
> [    5.310209]  [<c4040686>] warn_slowpath_fmt+0x26/0x30
> [    5.314358]  [<c403ca9c>] note_page+0x5ec/0x790
> [    5.318440]  [<c403cd8f>] ptdump_walk_pgd_level_core+0x14f/0x230
> [    5.322578]  [<c403ce91>] ptdump_walk_pgd_level_checkwx+0x11/0x20
> [    5.326632]  [<c4034ead>] mark_rodata_ro+0xcd/0xf0
> [    5.330625]  [<c4a4aab7>] kernel_init+0x17/0xc0
> [    5.334585]  [<c4a511c9>] ret_from_kernel_thread+0x21/0x38
> [    5.338585]  [<c4a4aaa0>] ? rest_init+0xa0/0xa0
> [    5.342583] ---[ end trace bc9ac0874ad9a058 ]---
> [    5.346630] x86/mm: Checked W+X mappings: FAILED, 5 W+X pages
> found.
> 
> ...I'm not quite sure why it does backtrace, or how to debug this
> one...
> 
> 									Pavel

-- 
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