vlan: fix memory leak in vlan_dev_set_egress_priority

There are few cases where the ndo_uninit() handler might be not
called if an error happens while device is initialized.

Since vlan_newlink() calls vlan_changelink() before
trying to register the netdevice, we need to make sure
vlan_dev_uninit() has been called at least once,
or we might leak allocated memory.

BUG: memory leak
unreferenced object 0xffff888122a206c0 (size 32):
  comm "syz-executor511", pid 7124, jiffies 4294950399 (age 32.240s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 61 73 00 00 00 00 00 00 00 00  ......as........
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<000000000eb3bb85>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline]
    [<000000000eb3bb85>] slab_post_alloc_hook mm/slab.h:586 [inline]
    [<000000000eb3bb85>] slab_alloc mm/slab.c:3320 [inline]
    [<000000000eb3bb85>] kmem_cache_alloc_trace+0x145/0x2c0 mm/slab.c:3549
    [<000000007b99f620>] kmalloc include/linux/slab.h:556 [inline]
    [<000000007b99f620>] vlan_dev_set_egress_priority+0xcc/0x150 net/8021q/vlan_dev.c:194
    [<000000007b0cb745>] vlan_changelink+0xd6/0x140 net/8021q/vlan_netlink.c:126
    [<0000000065aba83a>] vlan_newlink+0x135/0x200 net/8021q/vlan_netlink.c:181
    [<00000000fb5dd7a2>] __rtnl_newlink+0x89a/0xb80 net/core/rtnetlink.c:3305
    [<00000000ae4273a1>] rtnl_newlink+0x4e/0x80 net/core/rtnetlink.c:3363
    [<00000000decab39f>] rtnetlink_rcv_msg+0x178/0x4b0 net/core/rtnetlink.c:5424
    [<00000000accba4ee>] netlink_rcv_skb+0x61/0x170 net/netlink/af_netlink.c:2477
    [<00000000319fe20f>] rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5442
    [<00000000d51938dc>] netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
    [<00000000d51938dc>] netlink_unicast+0x223/0x310 net/netlink/af_netlink.c:1328
    [<00000000e539ac79>] netlink_sendmsg+0x2c0/0x570 net/netlink/af_netlink.c:1917
    [<000000006250c27e>] sock_sendmsg_nosec net/socket.c:639 [inline]
    [<000000006250c27e>] sock_sendmsg+0x54/0x70 net/socket.c:659
    [<00000000e2a156d1>] ____sys_sendmsg+0x2d0/0x300 net/socket.c:2330
    [<000000008c87466e>] ___sys_sendmsg+0x8a/0xd0 net/socket.c:2384
    [<00000000110e3054>] __sys_sendmsg+0x80/0xf0 net/socket.c:2417
    [<00000000d71077c8>] __do_sys_sendmsg net/socket.c:2426 [inline]
    [<00000000d71077c8>] __se_sys_sendmsg net/socket.c:2424 [inline]
    [<00000000d71077c8>] __x64_sys_sendmsg+0x23/0x30 net/socket.c:2424

Fixe: 07b5b17e ("[VLAN]: Use rtnl_link API")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/8021q/vlan.h

@@ -126,6 +126,7 @@ int vlan_check_real_dev(struct net_device *real_dev,
 void vlan_setup(struct net_device *dev);
 int register_vlan_dev(struct net_device *dev, struct netlink_ext_ack *extack);
 void unregister_vlan_dev(struct net_device *dev, struct list_head *head);
+void vlan_dev_uninit(struct net_device *dev);
 bool vlan_dev_inherit_address(struct net_device *dev,
 			      struct net_device *real_dev);
 

net/8021q/vlan_dev.c

@@ -586,7 +586,8 @@ static int vlan_dev_init(struct net_device *dev)
 	return 0;
 }
 
-static void vlan_dev_uninit(struct net_device *dev)
+/* Note: this function might be called multiple times for the same device. */
+void vlan_dev_uninit(struct net_device *dev)
 {
 	struct vlan_priority_tci_mapping *pm;
 	struct vlan_dev_priv *vlan = vlan_dev_priv(dev);

net/8021q/vlan_netlink.c

@@ -179,10 +179,11 @@ static int vlan_newlink(struct net *src_net, struct net_device *dev,
 		return -EINVAL;
 
 	err = vlan_changelink(dev, tb, data, extack);
-	if (err < 0)
+	if (!err)
+		err = register_vlan_dev(dev, extack);
+	if (err)
+		vlan_dev_uninit(dev);
 	return err;
-
-	return register_vlan_dev(dev, extack);
 }
 
 static inline size_t vlan_qos_map_size(unsigned int n)