[tip:irq/core] genirq: Fix null pointer reference in irq_set_affinity_hint()

[tip-bot for Jesse Brandeburg <tipbot@zytor.com>]

Commit-ID:  4fe7ffb7e17ca6ad9173b8de35f260c9c8fc2f79
Gitweb:     http://git.kernel.org/tip/4fe7ffb7e17ca6ad9173b8de35f260c9c8fc2f79
Author:     Jesse Brandeburg <jesse.brandeburg@intel.com>
AuthorDate: Wed, 28 Jan 2015 10:57:39 -0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Mon, 9 Feb 2015 18:47:42 +0100

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>
---
 kernel/irq/manage.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index f038e58..196a06f 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);