pktcdvd: fix BUG caused by sysfs module reference semantics change

pkt_setup_dev() expects module reference to be held on invocation.
This used to be true for sysfs callbacks but not anymore.  Test and
grab module reference around pkt_setup_dev() in
class_pktcdvd_store_add().

Signed-off-by: Tejun Heo <htejun@gmail.com>
Acked-by: Peter Osterlund <petero2@telia.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index a8130a4ad6d4..a5ee21319d37 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -358,10 +358,19 @@ static ssize_t class_pktcdvd_store_add(struct class *c, const char *buf,
                                         size_t count)
 {
         unsigned int major, minor;
+
         if (sscanf(buf, "%u:%u", &major, &minor) == 2) {
+                /* pkt_setup_dev() expects caller to hold reference to self */
+                if (!try_module_get(THIS_MODULE))
+                        return -ENODEV;
+
                 pkt_setup_dev(MKDEV(major, minor), NULL);
+
+                module_put(THIS_MODULE);
+
                 return count;
         }
+
         return -EINVAL;
 }