rxrpc: Fix memory leak in rxrpc_lookup_local

Commit 9ebeddef58 ("rxrpc: rxrpc_peer needs to hold a ref on the rxrpc_local record")
Then release ref in __rxrpc_put_peer and rxrpc_put_peer_locked.

	struct rxrpc_peer *rxrpc_alloc_peer(struct rxrpc_local *local, gfp_t gfp)
	-               peer->local = local;
	+               peer->local = rxrpc_get_local(local);

rxrpc_discard_prealloc also need ref release in discarding.

syzbot report:
BUG: memory leak
unreferenced object 0xffff8881080ddc00 (size 256):
  comm "syz-executor339", pid 8462, jiffies 4294942238 (age 12.350s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 0a 00 00 00 00 c0 00 08 81 88 ff ff  ................
  backtrace:
    [<000000002b6e495f>] kmalloc include/linux/slab.h:552 [inline]
    [<000000002b6e495f>] kzalloc include/linux/slab.h:682 [inline]
    [<000000002b6e495f>] rxrpc_alloc_local net/rxrpc/local_object.c:79 [inline]
    [<000000002b6e495f>] rxrpc_lookup_local+0x1c1/0x760 net/rxrpc/local_object.c:244
    [<000000006b43a77b>] rxrpc_bind+0x174/0x240 net/rxrpc/af_rxrpc.c:149
    [<00000000fd447a55>] afs_open_socket+0xdb/0x200 fs/afs/rxrpc.c:64
    [<000000007fd8867c>] afs_net_init+0x2b4/0x340 fs/afs/main.c:126
    [<0000000063d80ec1>] ops_init+0x4e/0x190 net/core/net_namespace.c:152
    [<00000000073c5efa>] setup_net+0xde/0x2d0 net/core/net_namespace.c:342
    [<00000000a6744d5b>] copy_net_ns+0x19f/0x3e0 net/core/net_namespace.c:483
    [<0000000017d3aec3>] create_new_namespaces+0x199/0x4f0 kernel/nsproxy.c:110
    [<00000000186271ef>] unshare_nsproxy_namespaces+0x9b/0x120 kernel/nsproxy.c:226
    [<000000002de7bac4>] ksys_unshare+0x2fe/0x5c0 kernel/fork.c:2957
    [<00000000349b12ba>] __do_sys_unshare kernel/fork.c:3025 [inline]
    [<00000000349b12ba>] __se_sys_unshare kernel/fork.c:3023 [inline]
    [<00000000349b12ba>] __x64_sys_unshare+0x12/0x20 kernel/fork.c:3023
    [<000000006d178ef7>] do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
    [<00000000637076d4>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

Fixes: 9ebeddef58 ("rxrpc: rxrpc_peer needs to hold a ref on the rxrpc_local record")
Signed-off-by: Takeshi Misawa <jeliantsurux@gmail.com>
Reported-and-tested-by: syzbot+305326672fed51b205f7@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/161183091692.3506637.3206605651502458810.stgit@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/rxrpc/call_accept.c

@@ -197,6 +197,7 @@ void rxrpc_discard_prealloc(struct rxrpc_sock *rx)
 	tail = b->peer_backlog_tail;
 	while (CIRC_CNT(head, tail, size) > 0) {
 		struct rxrpc_peer *peer = b->peer_backlog[tail];
+		rxrpc_put_local(peer->local);
 		kfree(peer);
 		tail = (tail + 1) & (size - 1);
 	}