Subject: [PATCH 02/38] mqprio: Fix out-of-bounds access in mqprio_dump

From: Vladyslav Tarasiuk <[email-masked]>
Date: Fri, 6 Dec 2019 13:51:05 +0000

[ Upstream commit 9f104c7736904ac72385bbb48669e0c923ca879b ]

When user runs a command like
tc qdisc add dev eth1 root mqprio
KASAN stack-out-of-bounds warning is emitted.
Currently, NLA_ALIGN macro used in mqprio_dump provides too large
buffer size as argument for nla_put and memcpy down the call stack.
The flow looks like this:
1. nla_put expects exact object size as an argument;
2. Later it provides this size to memcpy;
3. To calculate correct padding for SKB, nla_put applies NLA_ALIGN
   macro itself.

Therefore, NLA_ALIGN should not be applied to the nla_put parameter.
Otherwise it will lead to out-of-bounds memory access in memcpy.

Fixes: 4e8b86c06269 ("mqprio: Introduce new hardware offload mode and shaper in mqprio")
Signed-off-by: Vladyslav Tarasiuk <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/sched/sch_mqprio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
index 0d0113a24962..7b67e4d8e448 100644
--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -433,7 +433,7 @@ static int mqprio_dump(struct Qdisc *sch, struct sk_buff *skb)
 		opt.offset[tc] = dev->tc_to_txq[tc].offset;
 	}
 
-	if (nla_put(skb, TCA_OPTIONS, NLA_ALIGN(sizeof(opt)), &opt))
+	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
 		goto nla_put_failure;
 
 	if ((priv->flags & TC_MQPRIO_F_MODE) &&
-- 
2.20.1