Fix oops in acer_wmi driver (acer_wmi_init)

The acer_wmi driver does a DMI scan for quirks, and then sets flags into the
"interface" datastructure for some cases. However, the quirks happen real early
before "interface" is per se initialized from NULL.

The patch below 1) adds a NULL pointer check and 2) (re)runs the quirks at the
end, when "interface" has it's final value.

Reported-by: kerneloops.org
Acked-by: NCarlos Corbacho <carlos@strangeworlds.co.uk>
CC: stable@vger.kernel.org
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/misc/acer-wmi.c

@@ -192,6 +192,9 @@ static struct quirk_entry *quirks;
 
 static void set_quirks(void)
 {
+	if (!interface)
+		return;
+
 	if (quirks->mailled)
 		interface->capability |= ACER_CAP_MAILLED;
 
@@ -1237,6 +1240,8 @@ static int __init acer_wmi_init(void)
 		return -ENODEV;
 	}
 
+	set_quirks();
+
 	if (platform_driver_register(&acer_platform_driver)) {
 		printk(ACER_ERR "Unable to register platform driver.\n");
 		goto error_platform_register;