net/802/garp: fix memleak in garp_request_join()

I got kmemleak report when doing fuzz test:

BUG: memory leak
unreferenced object 0xffff88810c909b80 (size 64):
comm "syz", pid 957, jiffies 4295220394 (age 399.090s)
hex dump (first 32 bytes):
01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 08 00 00 00 01 02 00 04 ................
backtrace:
[<00000000ca1f2e2e>] garp_request_join+0x285/0x3d0
[<00000000bf153351>] vlan_gvrp_request_join+0x15b/0x190
[<0000000024005e72>] vlan_dev_open+0x706/0x980
[<00000000dc20c4d4>] __dev_open+0x2bb/0x460
[<0000000066573004>] __dev_change_flags+0x501/0x650
[<0000000035b42f83>] rtnl_configure_link+0xee/0x280
[<00000000a5e69de0>] __rtnl_newlink+0xed5/0x1550
[<00000000a5258f4a>] rtnl_newlink+0x66/0x90
[<00000000506568ee>] rtnetlink_rcv_msg+0x439/0xbd0
[<00000000b7eaeae1>] netlink_rcv_skb+0x14d/0x420
[<00000000c373ce66>] netlink_unicast+0x550/0x750
[<00000000ec74ce74>] netlink_sendmsg+0x88b/0xda0
[<00000000381ff246>] sock_sendmsg+0xc9/0x120
[<000000008f6a2db3>] ____sys_sendmsg+0x6e8/0x820
[<000000008d9c1735>] ___sys_sendmsg+0x145/0x1c0
[<00000000aa39dd8b>] __sys_sendmsg+0xfe/0x1d0

Calling garp_request_leave() after garp_request_join(), the attr->state
is set to GARP_APPLICANT_VO, garp_attr_destroy() won't be called in last
transmit event in garp_uninit_applicant(), the attr of applicant will be
leaked. To fix this leak, iterate and free each attr of applicant before
rerturning from garp_uninit_applicant().

Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: Yang Yingliang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/802/garp.c

···
 	kfree(attr);
 }
 
+static void garp_attr_destroy_all(struct garp_applicant *app)
+{
+	struct rb_node *node, *next;
+	struct garp_attr *attr;
+
+	for (node = rb_first(&app->gid);
+	     next = node ? rb_next(node) : NULL, node != NULL;
+	     node = next) {
+		attr = rb_entry(node, struct garp_attr, node);
+		garp_attr_destroy(app, attr);
+	}
+}
+
 static int garp_pdu_init(struct garp_applicant *app)
 {
 	struct sk_buff *skb;
···
 
 	spin_lock_bh(&app->lock);
 	garp_gid_event(app, GARP_EVENT_TRANSMIT_PDU);
+	garp_attr_destroy_all(app);
 	garp_pdu_queue(app);
 	spin_unlock_bh(&app->lock);