linux-kernel - [PATCH 5.18 192/339] amt: fix possible null-ptr-deref in amt

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Date:   Mon, 13 Jun 2022 12:10:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Taehee Yoo <ap420073@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.18 192/339] amt: fix possible null-ptr-deref in amt_rcv()

From: Taehee Yoo <ap420073@...il.com>

[ Upstream commit d16207f92a4a823c48b4ea953ad51f4483456768 ]

When amt interface receives amt message, it tries to obtain amt private
data from sock.
If there is no amt private data, it frees an skb immediately.
After kfree_skb(), it increases the rx_dropped stats.
But in order to use rx_dropped, amt private data is needed.
So, it makes amt_rcv() to do not increase rx_dropped stats when it can
not obtain amt private data.

Reported-by: kernel test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Fixes: 1a1a0e80e005 ("amt: fix possible memory leak in amt_rcv()")
Signed-off-by: Taehee Yoo <ap420073@...il.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/amt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/amt.c b/drivers/net/amt.c
index fbb03562cb95..2815db7ee2a3 100644
--- a/drivers/net/amt.c
+++ b/drivers/net/amt.c
@@ -2698,7 +2698,8 @@ static int amt_rcv(struct sock *sk, struct sk_buff *skb)
 	amt = rcu_dereference_sk_user_data(sk);
 	if (!amt) {
 		err = true;
-		goto drop;
+		kfree_skb(skb);
+		goto out;
 	}
 
 	skb->dev = amt->dev;
-- 
2.35.1