[PATCH] sched: address a potential NULL pointer dereference in the GRED scheduler.

[kwqcheii <juny24602@gmail.com>]

If kzalloc in gred_init returns a NULL pointer, the code follows the error handling path, invoking gred_destroy. This, in turn, calls gred_offload, where memset could receive a NULL pointer as input, potentially leading to a kernel crash.
---
 net/sched/sch_gred.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/sched/sch_gred.c b/net/sched/sch_gred.c
index ab6234b4fcd5..fa643e5709bd 100644
--- a/net/sched/sch_gred.c
+++ b/net/sched/sch_gred.c
@@ -317,10 +317,12 @@ static void gred_offload(struct Qdisc *sch, enum tc_gred_command command)
 	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
 		return;
 
-	memset(opt, 0, sizeof(*opt));
-	opt->command = command;
-	opt->handle = sch->handle;
-	opt->parent = sch->parent;
+	if (opt) {
+		memset(opt, 0, sizeof(*opt));
+		opt->command = command;
+		opt->handle = sch->handle;
+		opt->parent = sch->parent;
+	}
 
 	if (command == TC_GRED_REPLACE) {
 		unsigned int i;
-- 
2.48.1