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

Pavel Machek
2015-12-14T08:04:09Z

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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