linux-kernel - [PATCH 4.4 020/149] mlxsw: core: Increase scope of RCU read-side critical section

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Message-Id: <20200820092126.685237164@linuxfoundation.org>
Date:   Thu, 20 Aug 2020 11:21:37 +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, Ido Schimmel <idosch@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 020/149] mlxsw: core: Increase scope of RCU read-side critical section

From: Ido Schimmel <idosch@...lanox.com>

[ Upstream commit 7d8e8f3433dc8d1dc87c1aabe73a154978fb4c4d ]

The lifetime of the Rx listener item ('rxl_item') is managed using RCU,
but is dereferenced outside of RCU read-side critical section, which can
lead to a use-after-free.

Fix this by increasing the scope of the RCU read-side critical section.

Fixes: 93c1edb27f9e ("mlxsw: Introduce Mellanox switch driver core")
Signed-off-by: Ido Schimmel <idosch@...lanox.com>
Reviewed-by: Jiri Pirko <jiri@...lanox.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/mellanox/mlxsw/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlxsw/core.c b/drivers/net/ethernet/mellanox/mlxsw/core.c
index 97f0d93caf994..085aaad902937 100644
--- a/drivers/net/ethernet/mellanox/mlxsw/core.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core.c
@@ -1208,9 +1208,10 @@ void mlxsw_core_skb_receive(struct mlxsw_core *mlxsw_core, struct sk_buff *skb,
 			break;
 		}
 	}
-	rcu_read_unlock();
-	if (!found)
+	if (!found) {
+		rcu_read_unlock();
 		goto drop;
+	}
 
 	pcpu_stats = this_cpu_ptr(mlxsw_core->pcpu_stats);
 	u64_stats_update_begin(&pcpu_stats->syncp);
@@ -1221,6 +1222,7 @@ void mlxsw_core_skb_receive(struct mlxsw_core *mlxsw_core, struct sk_buff *skb,
 	u64_stats_update_end(&pcpu_stats->syncp);
 
 	rxl->func(skb, local_port, rxl_item->priv);
+	rcu_read_unlock();
 	return;
 
 drop:
-- 
2.25.1