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>

3 files changed, 6 insertions, 6 deletions

diff --git a/arch/x86/kernel/smp_32.c b/arch/x86/kernel/smp_32.c
index fcaa026eb807..d4c01a4aca60 100644
--- a/arch/x86/kernel/smp_32.c
+++ b/arch/x86/kernel/smp_32.c
@@ -223,7 +223,7 @@ void send_IPI_mask_sequence(cpumask_t mask, int vector)
          */ 
 
         local_irq_save(flags);
-        for (query_cpu = 0; query_cpu < NR_CPUS; ++query_cpu) {
+        for_each_possible_cpu(query_cpu) {
                 if (cpu_isset(query_cpu, mask)) {
                         __send_IPI_dest_field(cpu_to_logical_apicid(query_cpu),
                                               vector);
@@ -675,7 +675,7 @@ static int convert_apicid_to_cpu(int apic_id)
 {
         int i;
 
-        for (i = 0; i < NR_CPUS; i++) {
+        for_each_possible_cpu(i) {
                 if (per_cpu(x86_cpu_to_apicid, i) == apic_id)
                         return i;
         }
diff --git a/arch/x86/kernel/smpboot_32.c b/arch/x86/kernel/smpboot_32.c
index 239ada1c499c..0bf7f20baba0 100644
--- a/arch/x86/kernel/smpboot_32.c
+++ b/arch/x86/kernel/smpboot_32.c
@@ -1090,7 +1090,7 @@ static void __init smp_boot_cpus(unsigned int max_cpus)
          * Allow the user to impress friends.
          */
         Dprintk("Before bogomips.\n");
-        for (cpu = 0; cpu < NR_CPUS; cpu++)
+        for_each_possible_cpu(cpu)
                 if (cpu_isset(cpu, cpu_callout_map))
                         bogosum += cpu_data(cpu).loops_per_jiffy;
         printk(KERN_INFO
@@ -1121,7 +1121,7 @@ static void __init smp_boot_cpus(unsigned int max_cpus)
          * construct cpu_sibling_map, so that we can tell sibling CPUs
          * efficiently.
          */
-        for (cpu = 0; cpu < NR_CPUS; cpu++) {
+        for_each_possible_cpu(cpu) {
                 cpus_clear(per_cpu(cpu_sibling_map, cpu));
                 cpus_clear(per_cpu(cpu_core_map, cpu));
         }
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