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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "Suanming.Mou" <mousuanming@huawei.com>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        Stefano Brivio <sbrivio@redhat.com>,
        Zhiqiang Liu <liuzhiqiang26@huawei.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 12/56] vxlan: Dont call gro_cells_destroy() before device is unregistered
Date:   Mon,  1 Apr 2019 19:02:28 +0200
Message-Id: <20190401170104.595904744@linuxfoundation.org>
In-Reply-To: <20190401170103.398401360@linuxfoundation.org>
References: <20190401170103.398401360@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Zhiqiang Liu <liuzhiqiang26@huawei.com>

[ Upstream commit cc4807bb609230d8959fd732b0bf3bd4c2de8eac ]

Commit ad6c9986bcb62 ("vxlan: Fix GRO cells race condition between
receive and link delete") fixed a race condition for the typical case a vxlan
device is dismantled from the current netns. But if a netns is dismantled,
vxlan_destroy_tunnels() is called to schedule a unregister_netdevice_queue()
of all the vxlan tunnels that are related to this netns.

In vxlan_destroy_tunnels(), gro_cells_destroy() is called and finished before
unregister_netdevice_queue(). This means that the gro_cells_destroy() call is
done too soon, for the same reasons explained in above commit.

So we need to fully respect the RCU rules, and thus must remove the
gro_cells_destroy() call or risk use after-free.

Fixes: 58ce31cca1ff ("vxlan: GRO support at tunnel layer")
Signed-off-by: Suanming.Mou <mousuanming@huawei.com>
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/vxlan.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -3375,10 +3375,8 @@ static void __net_exit vxlan_exit_net(st
 		/* If vxlan->dev is in the same netns, it has already been added
 		 * to the list by the previous loop.
 		 */
-		if (!net_eq(dev_net(vxlan->dev), net)) {
-			gro_cells_destroy(&vxlan->gro_cells);
+		if (!net_eq(dev_net(vxlan->dev), net))
 			unregister_netdevice_queue(vxlan->dev, &list);
-		}
 	}
 
 	unregister_netdevice_many(&list);