fix: crash: IP: __bitmap_intersects+0x48/0x73
Ingo Molnar [Thu, 15 Jan 2009 14:46:08 +0000 (15:46 +0100)]
-tip testing found this crash:

> [   35.258515] calling  acpi_cpufreq_init+0x0/0x127 @ 1
> [   35.264127] BUG: unable to handle kernel NULL pointer dereference at (null)
> [   35.267554] IP: [<ffffffff80478092>] __bitmap_intersects+0x48/0x73
> [   35.267554] PGD 0
> [   35.267554] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC

arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c is still broken: there's no
allocation of the variable mask, so we pass in an uninitialized cmd.mask
field to drv_read(), which then passes it to the scheduler which then
crashes ...

Switch it over to the much simpler constant-cpumask-pointers approach.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c

index 5bf2c83..4b1c319 100644 (file)
@@ -145,7 +145,7 @@ typedef union {
 
 struct drv_cmd {
        unsigned int type;
-       cpumask_var_t mask;
+       const struct cpumask *mask;
        drv_addr_union addr;
        u32 val;
 };
@@ -231,6 +231,7 @@ static u32 get_cur_val(const struct cpumask *mask)
                return 0;
        }
 
+       cmd.mask = mask;
        drv_read(&cmd);
 
        dprintk("get_cur_val = %u\n", cmd.val);
@@ -397,9 +398,6 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
                return -ENODEV;
        }
 
-       if (unlikely(!alloc_cpumask_var(&cmd.mask, GFP_KERNEL)))
-               return -ENOMEM;
-
        perf = data->acpi_data;
        result = cpufreq_frequency_table_target(policy,
                                                data->freq_table,
@@ -444,9 +442,9 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
 
        /* cpufreq holds the hotplug lock, so we are safe from here on */
        if (policy->shared_type != CPUFREQ_SHARED_TYPE_ANY)
-               cpumask_and(cmd.mask, cpu_online_mask, policy->cpus);
+               cmd.mask = policy->cpus;
        else
-               cpumask_copy(cmd.mask, cpumask_of(policy->cpu));
+               cmd.mask = cpumask_of(policy->cpu);
 
        freqs.old = perf->states[perf->state].core_frequency * 1000;
        freqs.new = data->freq_table[next_state].frequency;
@@ -473,7 +471,6 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
        perf->state = next_perf_state;
 
 out:
-       free_cpumask_var(cmd.mask);
        return result;
 }