[SRU][M][PATCH 1/1] net: sched: sch_multiq: fix possible OOB write in multiq_tune()

[Koichiro Den]

From: Hangyu Hua <hbh25y at gmail.com>

q->bands will be assigned to qopt->bands to execute subsequent code logic
after kmalloc. So the old q->bands should not be used in kmalloc.
Otherwise, an out-of-bounds write will occur.

Fixes: c2999f7fb05b ("net: sched: multiq: don't call qdisc_put() while holding tree lock")
Signed-off-by: Hangyu Hua <hbh25y at gmail.com>
Acked-by: Cong Wang <cong.wang at bytedance.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit affc18fdc694190ca7575b9a86632a73b9fe043d)
CVE-2024-36978
Signed-off-by: Koichiro Den <koichiro.den at canonical.com>
---
 net/sched/sch_multiq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_multiq.c b/net/sched/sch_multiq.c
index 75c9c860182b..0d6649d937c9 100644
--- a/net/sched/sch_multiq.c
+++ b/net/sched/sch_multiq.c
@@ -185,7 +185,7 @@ static int multiq_tune(struct Qdisc *sch, struct nlattr *opt,
 
 	qopt->bands = qdisc_dev(sch)->real_num_tx_queues;
 
-	removed = kmalloc(sizeof(*removed) * (q->max_bands - q->bands),
+	removed = kmalloc(sizeof(*removed) * (q->max_bands - qopt->bands),
 			  GFP_KERNEL);
 	if (!removed)
 		return -ENOMEM;
-- 
2.43.0