vxlan: check vxlan_vnigroup_init() return value

vxlan_init() must check vxlan_vnigroup_init() success
otherwise a crash happens later, spotted by syzbot.

Oops: general protection fault, probably for non-canonical address 0xdffffc000000002c: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000160-0x0000000000000167]
CPU: 0 UID: 0 PID: 7313 Comm: syz-executor147 Not tainted 6.14.0-rc1-syzkaller-00276-g69b54314c975 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
 RIP: 0010:vxlan_vnigroup_uninit+0x89/0x500 drivers/net/vxlan/vxlan_vnifilter.c:912
Code: 00 48 8b 44 24 08 4c 8b b0 98 41 00 00 49 8d 86 60 01 00 00 48 89 c2 48 89 44 24 10 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 4d 04 00 00 49 8b 86 60 01 00 00 48 ba 00 00 00
RSP: 0018:ffffc9000cc1eea8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000001 RCX: ffffffff8672effb
RDX: 000000000000002c RSI: ffffffff8672ecb9 RDI: ffff8880461b4f18
RBP: ffff8880461b4ef4 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000020000
R13: ffff8880461b0d80 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fecfa95d6c0(0000) GS:ffff88806a600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fecfa95cfb8 CR3: 000000004472c000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  vxlan_uninit+0x1ab/0x200 drivers/net/vxlan/vxlan_core.c:2942
  unregister_netdevice_many_notify+0x12d6/0x1f30 net/core/dev.c:11824
  unregister_netdevice_many net/core/dev.c:11866 [inline]
  unregister_netdevice_queue+0x307/0x3f0 net/core/dev.c:11736
  register_netdevice+0x1829/0x1eb0 net/core/dev.c:10901
  __vxlan_dev_create+0x7c6/0xa30 drivers/net/vxlan/vxlan_core.c:3981
  vxlan_newlink+0xd1/0x130 drivers/net/vxlan/vxlan_core.c:4407
  rtnl_newlink_create net/core/rtnetlink.c:3795 [inline]
  __rtnl_newlink net/core/rtnetlink.c:3906 [inline]

Fixes: f9c4bb0 ("vxlan: vni filtering support on collect metadata device")
Reported-by: [email protected]
Closes: https://lore.kernel.org/netdev/[email protected]/T/#u
Signed-off-by: Eric Dumazet <[email protected]>
Cc: Roopa Prabhu <[email protected]>
Reviewed-by: Ido Schimmel <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Eric Dumazet

drivers/net/vxlan/vxlan_core.c

@@ -2898,8 +2898,11 @@ static int vxlan_init(struct net_device *dev)
 	struct vxlan_dev *vxlan = netdev_priv(dev);
 	int err;
 
-	if (vxlan->cfg.flags & VXLAN_F_VNIFILTER)
-		vxlan_vnigroup_init(vxlan);
+	if (vxlan->cfg.flags & VXLAN_F_VNIFILTER) {
+		err = vxlan_vnigroup_init(vxlan);
+		if (err)
+			return err;
+	}
 
 	err = gro_cells_init(&vxlan->gro_cells, dev);
 	if (err)