Re: 4.4-rc0: 5 W+X pages found

Mihai Donțu
2015-11-23T14:37:21Z

On Sun, 15 Nov 2015 08:00:22 +0100 Pavel Machek wrote:
> Kernel complains:
>
> [ 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...

That is a modest number.

[ 2.493559] ------------[ cut here ]------------
[ 2.493563] WARNING: CPU: 2 PID: 1 at arch/x86/mm/dump_pagetables.c:225 note_page+0x5e1/0x780()
[ 2.493565] x86/mm: Found insecure W+X mapping at address ffff88000009d000/0xffff88000009d000
[ 2.493565] Modules linked in:
[ 2.493568] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.4.0-rc2 #2
[ 2.493569] Hardware name: Dell Inc. Latitude E7440/07F3F4, BIOS A15 05/19/2015
[ 2.493570] 0000000000000000 00000000c03551f4 ffff88040c7cbd48 ffffffffaa54851c
[ 2.493572] ffff88040c7cbd90 ffff88040c7cbd80 ffffffffaa13a662 ffff88040c7cbe90
[ 2.493573] 8000000000000163 0000000000000004 0000000000000000 0000000000000000
[ 2.493575] Call Trace:
[ 2.493579] [<ffffffffaa54851c>] dump_stack+0x4e/0x82
[ 2.493582] [<ffffffffaa13a662>] warn_slowpath_common+0x82/0xc0
[ 2.493583] [<ffffffffaa13a6fc>] warn_slowpath_fmt+0x5c/0x80
[ 2.493585] [<ffffffffaa0a3f61>] note_page+0x5e1/0x780
[ 2.493587] [<ffffffffaa0a43c4>] ptdump_walk_pgd_level_core+0x2c4/0x3f0
[ 2.493588] [<ffffffffaa0a4527>] ptdump_walk_pgd_level_checkwx+0x17/0x20
[ 2.493591] [<ffffffffaa09ad0f>] mark_rodata_ro+0xef/0x100
[ 2.493594] [<ffffffffaae75d00>] ? rest_init+0x90/0x90
[ 2.493595] [<ffffffffaae75d1d>] kernel_init+0x1d/0xe0
[ 2.493596] [<ffffffffaae7c52f>] ret_from_fork+0x3f/0x70
[ 2.493598] [<ffffffffaae75d00>] ? rest_init+0x90/0x90
[ 2.493599] ---[ end trace e2aec56d15b94609 ]---
[ 2.498994] x86/mm: Checked W+X mappings: FAILED, 104640 W+X pages found.

All the while I have:

$ zgrep NX /proc/config.gz
CONFIG_DEBUG_SET_MODULE_RONX=y

I added to CC the people involved in pushing this feature to mainline,
maybe they can point me to a possible cause.

--
Mihai Donțu