netfilter: xt_cgroup: initialize info->priv in cgroup_mt_check_v1()

commit ba7cd5d95f25cc6005f687dabdb4e7a6063adda9 upstream.

xt_cgroup_info_v1->priv is an internal pointer only used for kernel,
we should not trust what user-space provides.

Reported-by: <syzbot+4fbcfcc0d2e6592bd641@syzkaller.appspotmail.com>
Fixes: c38c4597e4bf ("netfilter: implement xt_cgroup cgroup2 path match")
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/netfilter/xt_cgroup.c b/net/netfilter/xt_cgroup.c
index a086a91..0eddbd5 100644 (file)
--- a/net/netfilter/xt_cgroup.c
+++ b/net/netfilter/xt_cgroup.c
@@ -52,6 +52,7 @@ static int cgroup_mt_check_v1(const struct xt_mtchk_param *par)
                return -EINVAL;
        }
 
+       info->priv = NULL;
        if (info->has_path) {
                cgrp = cgroup_get_from_path(info->path);
                if (IS_ERR(cgrp)) {