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From:   Lin Ma <linma@zju.edu.cn>
To:     jk@codeconstruct.com.au, matt@codeconstruct.com.au,
        davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Lin Ma <linma@zju.edu.cn>
Subject: [PATCH v0] mctp: fix netdev reference bug
Date:   Thu, 24 Mar 2022 10:39:04 +0800
Message-Id: <20220324023904.7173-1-linma@zju.edu.cn>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

In extended addressing mode, function mctp_local_output() fetch netdev
through dev_get_by_index_rcu, which won't increase netdev's reference
counter. Hence, the reference may underflow when mctp_local_output calls
dev_put(), results in possible use after free.

This patch adds dev_hold() to fix the reference bug.

Fixes: 99ce45d5e7db ("mctp: Implement extended addressing")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
---
 net/mctp/route.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/mctp/route.c b/net/mctp/route.c
index e52cef750500..a9e5d6c40c65 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -817,6 +817,7 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
 			return rc;
 		}
 
+		dev_hold(dev);
 		rt->dev = __mctp_dev_get(dev);
 		rcu_read_unlock();
 
-- 
2.35.1