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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,
        syzbot+de73361ee4971b6e6f75@syzkaller.appspotmail.com,
        Hangbin Liu <liuhangbin@gmail.com>,
        Nikolay Aleksandrov <nikolay@cumulusnetworks.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 02/92] bridge: check iface upper dev when setting master via ioctl
Date:   Thu, 24 May 2018 11:37:39 +0200
Message-Id: <20180524093159.476457655@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Hangbin Liu <liuhangbin@gmail.com>

[ Upstream commit e8238fc2bd7b4c3c7554fa2df067e796610212fc ]

When we set a bond slave's master to bridge via ioctl, we only check
the IFF_BRIDGE_PORT flag. Although we will find the slave's real master
at netdev_master_upper_dev_link() later, it already does some settings
and allocates some resources. It would be better to return as early
as possible.

v1 -> v2:
use netdev_master_upper_dev_get() instead of netdev_has_any_upper_dev()
to check if we have a master, because not all upper devs are masters,
e.g. vlan device.

Reported-by: syzbot+de73361ee4971b6e6f75@syzkaller.appspotmail.com
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/bridge/br_if.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -456,8 +456,8 @@ int br_add_if(struct net_bridge *br, str
 	if (dev->netdev_ops->ndo_start_xmit == br_dev_xmit)
 		return -ELOOP;
 
-	/* Device is already being bridged */
-	if (br_port_exists(dev))
+	/* Device has master upper dev */
+	if (netdev_master_upper_dev_get(dev))
 		return -EBUSY;
 
 	/* No bridging devices that dislike that (e.g. wireless) */