linux-kernel - [PATCH 5.4 02/37] mqprio: Fix out-of-bounds access in mqprio

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Date:   Tue, 17 Dec 2019 21:09:23 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Vladyslav Tarasiuk <vladyslavt@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.4 02/37] mqprio: Fix out-of-bounds access in mqprio_dump

From: Vladyslav Tarasiuk <vladyslavt@...lanox.com>

[ 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 <vladyslavt@...lanox.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sched/sch_mqprio.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -433,7 +433,7 @@ static int mqprio_dump(struct Qdisc *sch
 		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) &&