[PATCH 4.15 17/45] netfilter: xt_cgroup: initialize info->priv in cgroup_mt_check_v1()

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Cong Wang <xiyou.wangcong@xxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxxxxxxxx>
Fixes: c38c4597e4bf ("netfilter: implement xt_cgroup cgroup2 path match")
Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/netfilter/xt_cgroup.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/netfilter/xt_cgroup.c
+++ b/net/netfilter/xt_cgroup.c
@@ -52,6 +52,7 @@ static int cgroup_mt_check_v1(const stru
 		return -EINVAL;
 	}
 
+	info->priv = NULL;
 	if (info->has_path) {
 		cgrp = cgroup_get_from_path(info->path);
 		if (IS_ERR(cgrp)) {