[CPUFREQ] cpumask: avoid cpumask games in arch/x86/kernel/cpu/cpufreq/speedstep-centr...

Impact: don't play with current's cpumask

It's generally a very bad idea to mug some process's cpumask: it could
legitimately and reasonably be changed by root, which could break us
(if done before our code) or them (if we restore the wrong value).

Use rdmsr_on_cpu and wrmsr_on_cpu instead.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
To: cpufreq@vger.kernel.org
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Dave Jones <davej@redhat.com>

diff --git a/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c b/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c
index 55c831e..8d672ef 100644 (file)
--- a/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c
+++ b/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c
@@ -323,14 +323,8 @@ static unsigned int get_cur_freq(unsigned int cpu)
 {
        unsigned l, h;
        unsigned clock_freq;
-       cpumask_t saved_mask;
 
-       saved_mask = current->cpus_allowed;
-       set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
-       if (smp_processor_id() != cpu)
-               return 0;
-
-       rdmsr(MSR_IA32_PERF_STATUS, l, h);
+       rdmsr_on_cpu(cpu, MSR_IA32_PERF_STATUS, &l, &h);
        clock_freq = extract_clock(l, cpu, 0);
 
        if (unlikely(clock_freq == 0)) {
@@ -340,11 +334,9 @@ static unsigned int get_cur_freq(unsigned int cpu)
                 * P-state transition (like TM2). Get the last freq set 
                 * in PERF_CTL.
                 */
-               rdmsr(MSR_IA32_PERF_CTL, l, h);
+               rdmsr_on_cpu(cpu, MSR_IA32_PERF_CTL, &l, &h);
                clock_freq = extract_clock(l, cpu, 1);
        }
-
-       set_cpus_allowed_ptr(current, &saved_mask);
        return clock_freq;
 }
 
@@ -467,15 +459,10 @@ static int centrino_target (struct cpufreq_policy *policy,
        struct cpufreq_freqs    freqs;
        int                     retval = 0;
        unsigned int            j, k, first_cpu, tmp;
-       cpumask_var_t saved_mask, covered_cpus;
+       cpumask_var_t covered_cpus;
 
-       if (unlikely(!alloc_cpumask_var(&saved_mask, GFP_KERNEL)))
-               return -ENOMEM;
-       if (unlikely(!zalloc_cpumask_var(&covered_cpus, GFP_KERNEL))) {
-               free_cpumask_var(saved_mask);
+       if (unlikely(!zalloc_cpumask_var(&covered_cpus, GFP_KERNEL)))
                return -ENOMEM;
-       }
-       cpumask_copy(saved_mask, &current->cpus_allowed);
 
        if (unlikely(per_cpu(centrino_model, cpu) == NULL)) {
                retval = -ENODEV;
@@ -493,7 +480,7 @@ static int centrino_target (struct cpufreq_policy *policy,
 
        first_cpu = 1;
        for_each_cpu(j, policy->cpus) {
-               const struct cpumask *mask;
+               int good_cpu;
 
                /* cpufreq holds the hotplug lock, so we are safe here */
                if (!cpu_online(j))
@@ -504,32 +491,30 @@ static int centrino_target (struct cpufreq_policy *policy,
                 * Make sure we are running on CPU that wants to change freq
                 */
                if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY)
-                       mask = policy->cpus;
+                       good_cpu = cpumask_any_and(policy->cpus,
+                                                  cpu_online_mask);
                else
-                       mask = cpumask_of(j);
+                       good_cpu = j;
 
-               set_cpus_allowed_ptr(current, mask);
-               preempt_disable();
-               if (unlikely(!cpu_isset(smp_processor_id(), *mask))) {
+               if (good_cpu >= nr_cpu_ids) {
                        dprintk("couldn't limit to CPUs in this domain\n");
                        retval = -EAGAIN;
                        if (first_cpu) {
                                /* We haven't started the transition yet. */
-                               goto migrate_end;
+                               goto out;
                        }
-                       preempt_enable();
                        break;
                }
 
                msr = per_cpu(centrino_model, cpu)->op_points[newstate].index;
 
                if (first_cpu) {
-                       rdmsr(MSR_IA32_PERF_CTL, oldmsr, h);
+                       rdmsr_on_cpu(good_cpu, MSR_IA32_PERF_CTL, &oldmsr, &h);
                        if (msr == (oldmsr & 0xffff)) {
                                dprintk("no change needed - msr was and needs "
                                        "to be %x\n", oldmsr);
                                retval = 0;
-                               goto migrate_end;
+                               goto out;
                        }
 
                        freqs.old = extract_clock(oldmsr, cpu, 0);
@@ -553,14 +538,11 @@ static int centrino_target (struct cpufreq_policy *policy,
                        oldmsr |= msr;
                }
 
-               wrmsr(MSR_IA32_PERF_CTL, oldmsr, h);
-               if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY) {
-                       preempt_enable();
+               wrmsr_on_cpu(good_cpu, MSR_IA32_PERF_CTL, oldmsr, h);
+               if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY)
                        break;
-               }
 
-               cpu_set(j, *covered_cpus);
-               preempt_enable();
+               cpumask_set_cpu(j, covered_cpus);
        }
 
        for_each_cpu(k, policy->cpus) {
@@ -578,10 +560,8 @@ static int centrino_target (struct cpufreq_policy *policy,
                 * Best effort undo..
                 */
 
-               for_each_cpu_mask_nr(j, *covered_cpus) {
-                       set_cpus_allowed_ptr(current, &cpumask_of_cpu(j));
-                       wrmsr(MSR_IA32_PERF_CTL, oldmsr, h);
-               }
+               for_each_cpu(j, covered_cpus)
+                       wrmsr_on_cpu(j, MSR_IA32_PERF_CTL, oldmsr, h);
 
                tmp = freqs.new;
                freqs.new = freqs.old;
@@ -593,15 +573,9 @@ static int centrino_target (struct cpufreq_policy *policy,
                        cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
                }
        }
-       set_cpus_allowed_ptr(current, saved_mask);
        retval = 0;
-       goto out;
 
-migrate_end:
-       preempt_enable();
-       set_cpus_allowed_ptr(current, saved_mask);
 out:
-       free_cpumask_var(saved_mask);
        free_cpumask_var(covered_cpus);
        return retval;
 }