netfilter: nft_set_rbtree: fix parameter of __nft_rbtree_lookup()

The parameter this doesn't have a flags value. so that it can't be
used by nft_rbtree_interval_end().

test commands:
   %nft add table ip filter
   %nft add set ip filter s { type ipv4_addr \; flags interval \; }
   %nft add element ip filter s {0-1}
   %nft add element ip filter s {2-10}
   %nft add chain ip filter input { type filter hook input priority 0\; }
   %nft add rule ip filter input ip saddr @s

Splat looks like:
[  246.752502] BUG: KASAN: slab-out-of-bounds in __nft_rbtree_lookup+0x677/0x6a0 [nft_set_rbtree]
[  246.752502] Read of size 1 at addr ffff88010d9efa47 by task http/1092

[  246.752502] CPU: 1 PID: 1092 Comm: http Not tainted 4.17.0-rc6+ #185
[  246.752502] Call Trace:
[  246.752502]  <IRQ>
[  246.752502]  dump_stack+0x74/0xbb
[  246.752502]  ? __nft_rbtree_lookup+0x677/0x6a0 [nft_set_rbtree]
[  246.752502]  print_address_description+0xc7/0x290
[  246.752502]  ? __nft_rbtree_lookup+0x677/0x6a0 [nft_set_rbtree]
[  246.752502]  kasan_report+0x22c/0x350
[  246.752502]  __nft_rbtree_lookup+0x677/0x6a0 [nft_set_rbtree]
[  246.752502]  nft_rbtree_lookup+0xc9/0x2d2 [nft_set_rbtree]
[  246.752502]  ? sched_clock_cpu+0x144/0x180
[  246.752502]  nft_lookup_eval+0x149/0x3a0 [nf_tables]
[  246.752502]  ? __lock_acquire+0xcea/0x4ed0
[  246.752502]  ? nft_lookup_init+0x6b0/0x6b0 [nf_tables]
[  246.752502]  nft_do_chain+0x263/0xf50 [nf_tables]
[  246.752502]  ? __nft_trace_packet+0x1a0/0x1a0 [nf_tables]
[  246.752502]  ? sched_clock_cpu+0x144/0x180
[ ... ]

Fixes: f9121355eb6f ("netfilter: nft_set_rbtree: incorrect assumption on lower interval lookups")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nft_set_rbtree.c

@@ -65,7 +65,7 @@ static bool __nft_rbtree_lookup(const struct net *net, const struct nft_set *set
 			parent = rcu_dereference_raw(parent->rb_left);
 			if (interval &&
 			    nft_rbtree_equal(set, this, interval) &&
-			    nft_rbtree_interval_end(this) &&
+			    nft_rbtree_interval_end(rbe) &&
 			    !nft_rbtree_interval_end(interval))
 				continue;
 			interval = rbe;