[PATCH net-next] net: core: fix the order in dev_put() and rtnl_lock()

The dev_put() should be after rtnl_lock() in case for race.

Fixes: 893b19587534 ("net: bridge: fix ioctl locking")
Signed-off-by: Yajun Deng <redacted>
---
 net/core/dev_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 0e87237fd871..9796fa35fe88 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c

@@ -384,8 +384,8 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, void __user *data,
 		dev_hold(dev);
 		rtnl_unlock();
 		err = br_ioctl_call(net, netdev_priv(dev), cmd, ifr, NULL);
-		dev_put(dev);
 		rtnl_lock();
+		dev_put(dev);
 		return err;
 
 	case SIOCSHWTSTAMP:

-- 
2.32.0

On 9/13/21 8:01 PM, Yajun Deng wrote:

What race exactly are you trying to avoid ?

This patch does not look needed to me.

On 14/09/2021 08:18, Eric Dumazet wrote:

On 9/13/21 8:01 PM, Yajun Deng wrote:

quoted

The dev_put() should be after rtnl_lock() in case for race.

Fixes: 893b19587534 ("net: bridge: fix ioctl locking")
Signed-off-by: Yajun Deng <redacted>
---
 net/core/dev_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index 0e87237fd871..9796fa35fe88 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c

@@ -384,8 +384,8 @@ static int dev_ifsioc(struct net *net, struct ifreq *ifr, void __user *data,
 		dev_hold(dev);
 		rtnl_unlock();
 		err = br_ioctl_call(net, netdev_priv(dev), cmd, ifr, NULL);
-		dev_put(dev);
 		rtnl_lock();
+		dev_put(dev);
 		return err;
 
 	case SIOCSHWTSTAMP:

What race exactly are you trying to avoid ?

This patch does not look needed to me.

+1 

There isn't a race there