x86/irq: Validate that irq descriptor is still active

In fixup_irqs() we unconditionally dereference the irq chip of an irq
descriptor. The descriptor might still be valid, but already cleaned up,
i.e. the chip removed. Add a check for this condition.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Joe Lawrence <joe.lawrence@stratus.com>
Cc: Jeremiah Mahler <jmmahler@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: andy.shevchenko@gmail.com
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: stable@vger.kernel.org #4.3+
Link: http://lkml.kernel.org/r/20151231160106.236423282@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index f8062aa..c0b58dd 100644 (file)
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -470,6 +470,15 @@ void fixup_irqs(void)
                }
 
                chip = irq_data_get_irq_chip(data);
+               /*
+                * The interrupt descriptor might have been cleaned up
+                * already, but it is not yet removed from the radix tree
+                */
+               if (!chip) {
+                       raw_spin_unlock(&desc->lock);
+                       continue;
+               }
+
                if (!irqd_can_move_in_process_context(data) && chip->irq_mask)
                        chip->irq_mask(data);