[Patch net] netfilter: fix a use-after-free in mtype_destroy()

[Patch net] netfilter: fix a use-after-free in mtype_destroy()

[Cong Wang]

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@syzkaller.appspotmail.com
Fixes: 40cd63bf33b2 ("netfilter: ipset: Support extensions which need a per data destroy function")
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 net/netfilter/ipset/ip_set_bitmap_gen.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/ipset/ip_set_bitmap_gen.h b/net/netfilter/ipset/ip_set_bitmap_gen.h
index 1abd6f0dc227..077a2cb65fcb 100644
--- a/net/netfilter/ipset/ip_set_bitmap_gen.h
+++ b/net/netfilter/ipset/ip_set_bitmap_gen.h
@@ -60,9 +60,9 @@ mtype_destroy(struct ip_set *set)
 	if (SET_WITH_TIMEOUT(set))
 		del_timer_sync(&map->gc);
 
-	ip_set_free(map->members);
 	if (set->dsize && set->extensions & IPSET_EXT_DESTROY)
 		mtype_ext_cleanup(set);
+	ip_set_free(map->members);
 	ip_set_free(map);
 
 	set->data = NULL;
-- 
2.21.1

Re: [Patch net] netfilter: fix a use-after-free in mtype_destroy()

[Pablo Neira Ayuso]

On Fri, Jan 10, 2020 at 11:53:08AM -0800, Cong Wang wrote:
> 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.

Applied, thanks.