net-sysfs: Fix reference count leak in rx|netdev_queue_add_kobject

kobject_init_and_add takes reference even when it fails. This has
to be given up by the caller in error handling. Otherwise memory
allocated by kobject_init_and_add is never freed. Originally found
by Syzkaller:

BUG: memory leak
unreferenced object 0xffff8880679f8b08 (size 8):
  comm "netdev_register", pid 269, jiffies 4294693094 (age 12.132s)
  hex dump (first 8 bytes):
    72 78 2d 30 00 36 20 d4                          rx-0.6 .
  backtrace:
    [<000000008c93818e>] __kmalloc_track_caller+0x16e/0x290
    [<000000001f2e4e49>] kvasprintf+0xb1/0x140
    [<000000007f313394>] kvasprintf_const+0x56/0x160
    [<00000000aeca11c8>] kobject_set_name_vargs+0x5b/0x140
    [<0000000073a0367c>] kobject_init_and_add+0xd8/0x170
    [<0000000088838e4b>] net_rx_queue_update_kobjects+0x152/0x560
    [<000000006be5f104>] netdev_register_kobject+0x210/0x380
    [<00000000e31dab9d>] register_netdevice+0xa1b/0xf00
    [<00000000f68b2465>] __tun_chr_ioctl+0x20d5/0x3dd0
    [<000000004c50599f>] tun_chr_ioctl+0x2f/0x40
    [<00000000bbd4c317>] do_vfs_ioctl+0x1c7/0x1510
    [<00000000d4c59e8f>] ksys_ioctl+0x99/0xb0
    [<00000000946aea81>] __x64_sys_ioctl+0x78/0xb0
    [<0000000038d946e5>] do_syscall_64+0x16f/0x580
    [<00000000e0aa5d8f>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
    [<00000000285b3d1a>] 0xffffffffffffffff

Cc: David Miller <davem@davemloft.net>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Jouni Hogander <jouni.hogander@unikie.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/net-sysfs.c

@@ -923,21 +923,23 @@ static int rx_queue_add_kobject(struct net_device *dev, int index)
 	error = kobject_init_and_add(kobj, &rx_queue_ktype, NULL,
 				     "rx-%u", index);
 	if (error)
-		return error;
+		goto err;
 
 	dev_hold(queue->dev);
 
 	if (dev->sysfs_rx_queue_group) {
 		error = sysfs_create_group(kobj, dev->sysfs_rx_queue_group);
-		if (error) {
-			kobject_put(kobj);
-			return error;
-		}
+		if (error)
+			goto err;
 	}
 
 	kobject_uevent(kobj, KOBJ_ADD);
 
 	return error;
+
+err:
+	kobject_put(kobj);
+	return error;
 }
 #endif /* CONFIG_SYSFS */
 
@@ -1461,21 +1463,21 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index)
 	error = kobject_init_and_add(kobj, &netdev_queue_ktype, NULL,
 				     "tx-%u", index);
 	if (error)
-		return error;
+		goto err;
 
 	dev_hold(queue->dev);
 
 #ifdef CONFIG_BQL
 	error = sysfs_create_group(kobj, &dql_group);
-	if (error) {
-		kobject_put(kobj);
-		return error;
-	}
+	if (error)
+		goto err;
 #endif
 
 	kobject_uevent(kobj, KOBJ_ADD);
 
-	return 0;
+err:
+	kobject_put(kobj);
+	return error;
 }
 #endif /* CONFIG_SYSFS */