linux-kernel - [PATCH 3.16 178/245] netfilter: fix a use-after-free in mtype

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Date:   Fri, 24 Apr 2020 00:06:45 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Pablo Neira Ayuso" <pablo@...filter.org>,
        syzbot+4c3cc6dbe7259dbf9054@...kaller.appspotmail.com,
        "Jozsef Kadlecsik" <kadlec@...filter.org>,
        "Cong Wang" <xiyou.wangcong@...il.com>
Subject: [PATCH 3.16 178/245] netfilter: fix a use-after-free in
 mtype_destroy()

3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Cong Wang <xiyou.wangcong@...il.com>

commit c120959387efa51479056fd01dc90adfba7a590c upstream.

map->members is freed by ip_set_free() right before using it in
mtype_ext_cleanup() again. So we just have to move it down.

Reported-by: syzbot+4c3cc6dbe7259dbf9054@...kaller.appspotmail.com
Fixes: 40cd63bf33b2 ("netfilter: ipset: Support extensions which need a per data destroy function")
Acked-by: Jozsef Kadlecsik <kadlec@...filter.org>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/netfilter/ipset/ip_set_bitmap_gen.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/netfilter/ipset/ip_set_bitmap_gen.h
+++ b/net/netfilter/ipset/ip_set_bitmap_gen.h
@@ -66,12 +66,12 @@ mtype_destroy(struct ip_set *set)
 	if (SET_WITH_TIMEOUT(set))
 		del_timer_sync(&map->gc);
 
-	ip_set_free(map->members);
 	if (set->dsize) {
 		if (set->extensions & IPSET_EXT_DESTROY)
 			mtype_ext_cleanup(set);
 		ip_set_free(map->extensions);
 	}
+	ip_set_free(map->members);
 	kfree(map);
 
 	set->data = NULL;