linux-kernel - [ 07/21] x86: Fix bit corruption at CPU resume time

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Date:	Wed, 22 May 2013 15:10:25 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Peter Anvin <hpa@...ux.intel.com>,
	Fernando Luis Vázquez Cao 
	<fernando@....ntt.co.jp>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 07/21] x86: Fix bit corruption at CPU resume time

3.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Linus Torvalds <torvalds@...ux-foundation.org>

commit 5e427ec2d066b48a5c27b3a5a3315f7e4e729077 upstream.

In commit 78d77df71510 ("x86-64, init: Do not set NX bits on non-NX
capable hardware") we added the early_pmd_flags that gets the NX bit set
when a CPU supports NX. However, the new variable was marked __initdata,
because the main _use_ of this is in an __init routine.

However, the bit setting happens from secondary_startup_64(), which is
called not only at bootup, but on every secondary CPU start.  Including
resuming from STR and at CPU hotplug time.  So the value cannot be
__initdata.

Reported-bisected-and-tested-by: Michal Hocko <mhocko@...e.cz>
Acked-by: Peter Anvin <hpa@...ux.intel.com>
Cc: Fernando Luis Vázquez Cao <fernando@....ntt.co.jp>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/head64.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -34,7 +34,7 @@
 extern pgd_t early_level4_pgt[PTRS_PER_PGD];
 extern pmd_t early_dynamic_pgts[EARLY_DYNAMIC_PAGE_TABLES][PTRS_PER_PMD];
 static unsigned int __initdata next_early_pgt = 2;
-pmdval_t __initdata early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
+pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
 
 /* Wipe all early page tables except for the kernel symbol map */
 static void __init reset_early_page_tables(void)


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