ARM: perf_event_cpu.c: fix memory corruption causing unpleasant effects

1) The memory obtained via alloc_percpu() is defined (and zeroed) only
   for those CPUs in cpu_possible_mask.  For example, it is wrong to
   itterate using:

       for (i = 0; i < NR_CPUS; i++)
           per_cpu_ptr(cpu_pmus, i)->mpidr = -1;

   This is guaranteed to corrupt memory for those CPU numbers not marked
   possible during CPU enumeration.

2) In cpu_pmu_free_irq(), an occasional  cpu_pmu->mpidr of -1 (meaning
   uninitialized) was nevertheless passed to find_logical_cpu() which
   ended up returning very creative CPU numbers.  This was then used
   with this line:

       if (!cpumask_test_and_clear_cpu(cpu, &pmu->active_irqs))

   This corrupted memory due to the pmu->active_irqs overflow, and
   provided rather random condition results.

What made this bug even nastier is the fact that a slight change in code
placement due to compiler version, kernel config options or even added
debugging traces  could totally change the bug symptom.

Signed-off-by: Nicolas Pitre <nico@linaro.org>

0 files changed, 0 insertions, 0 deletions