ieee1394: fix NULL pointer dereference in sysfs access

Regression since "ieee1394: prevent device binding of raw1394,
video1394, dv1394", commit d2ace29fa44589da51fedc06a67b3f05301f3bfd:
$ cat /sys/bus/ieee1394/drivers/raw1394/device_ids
triggers a NULL pointer dereference in fw_show_drv_device_ids.
Reported by Miles Lane.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Tested-by: Miles Lane <miles.lane@gmail.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/ieee1394/nodemgr.c b/drivers/ieee1394/nodemgr.c
index 70afa3786f3..c6babe802a3 100644
--- a/drivers/ieee1394/nodemgr.c
+++ b/drivers/ieee1394/nodemgr.c
@@ -520,8 +520,11 @@ static ssize_t fw_show_drv_device_ids(struct device_driver *drv, char *buf)
         char *scratch = buf;
 
         driver = container_of(drv, struct hpsb_protocol_driver, driver);
+        id = driver->id_table;
+        if (!id)
+                return 0;
 
-        for (id = driver->id_table; id->match_flags != 0; id++) {
+        for (; id->match_flags != 0; id++) {
                 int need_coma = 0;
 
                 if (id->match_flags & IEEE1394_MATCH_VENDOR_ID) {