[PATCH] net: sched: sch_multiq: fix possible OOB write in multiq_tune()

From: Hangyu Hua
Date: Mon Jun 03 2024 - 03:15:25 EST


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@xxxxxxxxx>
---
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 79e93a19d5fa..06e03f5cd7ce 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;
--
2.34.1