[net PATCH] net: sched: Fix one possible panic when no destroy callback

From: Gao Feng <redacted>

When qdisc fail to init, qdisc_create would invoke the destroy callback
to cleanup. But there is no check if the callback exists really. So it
would cause the panic if there is no real destroy callback like these
qdisc codel, pfifo, pfifo_fast, and so on.

Now add one the check for destroy to avoid the possible panic.

Signed-off-by: Gao Feng <redacted>
---
 net/sched/sch_api.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index e88342f..cfdbfa1 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c

@@ -1019,7 +1019,8 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 		return sch;
 	}
 	/* ops->init() failed, we call ->destroy() like qdisc_create_dflt() */
-	ops->destroy(sch);
+	if (ops->destroy)
+		ops->destroy(sch);
 err_out3:
 	dev_put(dev);
 	kfree((char *) sch - sch->padded);

-- 
1.9.1