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

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Message-ID: <20151215213359.GM25973@pd.tnic>
Date:	Tue, 15 Dec 2015 22:33:59 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Pavel Machek <pavel@....cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Anvin <hpa@...or.com>, Mike Galbraith <efault@....de>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: 4.4-rc5: ugly warn on: 5 W+X pages found

On Tue, Dec 15, 2015 at 09:58:35PM +0100, Pavel Machek wrote:
> [    0.000000] Base memory trampoline at [c009b000] 9b000 size 16384
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] WARNING: CPU: 0 PID: 0 at
> ./arch/x86/include/asm/pgtable.h:357 kernel_physical_mapping_init+0x
> 256/0x395()
> [    0.000000] Modules linked in:
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.4.0-rc5+ #137
> [    0.000000] Hardware name: LENOVO 17097HU/17097HU, BIOS 7BETD8WW
> (2.19 ) 03/31/2011
> [    0.000000]  00000000 00000000 c4e63e90 c42baaf8 00000000 c4e63eac
> c404066b 00000165
> [    0.000000]  c4f134da 00000000 00000000 00000000 c4e63ebc c404070f
> 00000009 00000000
> [    0.000000]  c4e63f18 c4f134da c4e63f00 00000000 00000000 00000000
> 00000000 00000000
> [    0.000000] Call Trace:
> [    0.000000]  [<c42baaf8>] dump_stack+0x41/0x59
> [    0.000000]  [<c404066b>] warn_slowpath_common+0x6b/0xa0
> [    0.000000]  [<c4f134da>] ?
> kernel_physical_mapping_init+0x256/0x395
> [    0.000000]  [<c404070f>] warn_slowpath_null+0xf/0x20
> [    0.000000]  [<c4f134da>] kernel_physical_mapping_init+0x256/0x395
> [    0.000000]  [<c4a4de21>] init_memory_mapping+0x191/0x300
> [    0.000000]  [<c4f12d96>] init_mem_mapping+0xe7/0x1f3

Looks like the ISA range to me:

init_mem_mapping:

	...

        /* the ISA range is always mapped regardless of memory holes */
        init_memory_mapping(0, ISA_END_ADDRESS);

Does that kernel_physical_mapping_init() even pay attention to
__supported_pte_mask and thus _PAGE_NX? I don't see it.

Hmm, not really:

	pgprot_t init_prot = __pgprot(PTE_IDENT_ATTR | _PAGE_PSE);

	...

	prot = PAGE_KERNEL_LARGE_EXEC;

	...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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