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

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>

1 files changed, 17 insertions, 43 deletions

diff --git a/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c b/arch/x86/kernel/cpu/cpufreq/speedstep-centrino.c
index 55c831ed71ce..8d672ef162ce 100644
--- 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;
 }