x86: prevent dereferencing non-allocated per_cpu variables

'for_each_possible_cpu(i)' when there's a _remote possibility_ of
dereferencing a non-allocated per_cpu variable involved.

All files except mm/vmstat.c are x86 arch.

Thanks to pageexec@freemail.hu for pointing this out.

Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: <pageexec@freemail.hu>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index c1b131bcdcbe..8e1234e14559 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -146,7 +146,7 @@ void __init xen_smp_prepare_boot_cpu(void)
            old memory can be recycled */
         make_lowmem_page_readwrite(&per_cpu__gdt_page);
 
-        for (cpu = 0; cpu < NR_CPUS; cpu++) {
+        for_each_possible_cpu(cpu) {
                 cpus_clear(per_cpu(cpu_sibling_map, cpu));
                 /*
                  * cpu_core_map lives in a per cpu area that is cleared
@@ -163,7 +163,7 @@ void __init xen_smp_prepare_cpus(unsigned int max_cpus)
 {
         unsigned cpu;
 
-        for (cpu = 0; cpu < NR_CPUS; cpu++) {
+        for_each_possible_cpu(cpu) {
                 cpus_clear(per_cpu(cpu_sibling_map, cpu));
                 /*
                  * cpu_core_ map will be zeroed when the per