genirq: Fix null pointer reference in irq_set_affinity_hint()

The recent set_affinity commit by me introduced some null
pointer dereferences on driver unload, because some drivers
call this function with a NULL argument. This fixes the issue
by just checking for null before setting the affinity mask.

Fixes: e2e64a932556 ("genirq: Set initial affinity in irq_set_affinity_hint()")
Reported-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
CC: netdev@vger.kernel.org
Link: http://lkml.kernel.org/r/20150128185739.9689.84588.stgit@jbrandeb-cp2.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index f038e586a4b9..196a06fbc122 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -244,7 +244,8 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
         desc->affinity_hint = m;
         irq_put_desc_unlock(desc, flags);
         /* set the initial affinity to prevent every interrupt being on CPU0 */
-        __irq_set_affinity(irq, m, false);
+        if (m)
+                __irq_set_affinity(irq, m, false);
         return 0;
 }
 EXPORT_SYMBOL_GPL(irq_set_affinity_hint);