net: fix bridge notify hook to manage flags correctly

The bridge notify hook rtnl_bridge_notify() was not handling the
case where the master flags was set or with both flags set. First
flags are not being passed correctly and second the logic to parse
them is broken.

This patch passes the original flags value and fixes the
logic.

Reported-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a0e3507..04a201a 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2364,13 +2364,19 @@
 		goto errout;
 	}
 
-	if (!flags && master && master->netdev_ops->ndo_bridge_getlink)
+	if ((!flags || (flags & BRIDGE_FLAGS_MASTER)) &&
+	    master && master->netdev_ops->ndo_bridge_getlink) {
 		err = master->netdev_ops->ndo_bridge_getlink(skb, 0, 0, dev);
-	else if (dev->netdev_ops->ndo_bridge_getlink)
-		err = dev->netdev_ops->ndo_bridge_getlink(skb, 0, 0, dev);
+		if (err < 0)
+			goto errout;
+	}
 
-	if (err < 0)
-		goto errout;
+	if ((flags & BRIDGE_FLAGS_SELF) &&
+	    dev->netdev_ops->ndo_bridge_getlink) {
+		err = dev->netdev_ops->ndo_bridge_getlink(skb, 0, 0, dev);
+		if (err < 0)
+			goto errout;
+	}
 
 	rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL, GFP_ATOMIC);
 	return 0;
@@ -2389,7 +2395,8 @@
 	struct net_device *dev;
 	struct nlattr *br_spec, *attr = NULL;
 	int rem, err = -EOPNOTSUPP;
-	u16 flags = 0;
+	u16 oflags, flags = 0;
+	bool have_flags = false;
 
 	if (nlmsg_len(nlh) < sizeof(*ifm))
 		return -EINVAL;
@@ -2408,12 +2415,15 @@
 	if (br_spec) {
 		nla_for_each_nested(attr, br_spec, rem) {
 			if (nla_type(attr) == IFLA_BRIDGE_FLAGS) {
+				have_flags = true;
 				flags = nla_get_u16(attr);
 				break;
 			}
 		}
 	}
 
+	oflags = flags;
+
 	if (!flags || (flags & BRIDGE_FLAGS_MASTER)) {
 		if (!dev->master ||
 		    !dev->master->netdev_ops->ndo_bridge_setlink) {
@@ -2438,11 +2448,11 @@
 			flags &= ~BRIDGE_FLAGS_SELF;
 	}
 
-	if (attr && nla_type(attr) == IFLA_BRIDGE_FLAGS)
+	if (have_flags)
 		memcpy(nla_data(attr), &flags, sizeof(flags));
 	/* Generate event to notify upper layer of bridge change */
 	if (!err)
-		err = rtnl_bridge_notify(dev, flags);
+		err = rtnl_bridge_notify(dev, oflags);
 out:
 	return err;
 }