In tcf_connmark_dump(), the variable 'opt' was partially initialized using a
designatied initializer. While the padding bytes are reamined
uninitialized. nla_put() copies the entire structure into a
netlink message, these uninitialized bytes leaked to userspace.

Initialize the structure with memset before assigning its fields
to ensure all members and padding are cleared prior to beign copied.

Reported-by: syzbot+0c85cae3350b7d486aee@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=0c85cae3350b7d486aee
Tested-by: syzbot+0c85cae3350b7d486aee@syzkaller.appspotmail.com
Fixes: 22a5dc0e5e3e ("net: sched: Introduce connmark action")
Signed-off-by: Ranganath V N <redacted>
---
 net/sched/act_connmark.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/sched/act_connmark.c b/net/sched/act_connmark.c
index 3e89927d7116..26ba8c2d20ab 100644
--- a/net/sched/act_connmark.c
+++ b/net/sched/act_connmark.c

@@ -195,13 +195,15 @@ static inline int tcf_connmark_dump(struct sk_buff *skb, struct tc_action *a,
 	const struct tcf_connmark_info *ci = to_connmark(a);
 	unsigned char *b = skb_tail_pointer(skb);
 	const struct tcf_connmark_parms *parms;
-	struct tc_connmark opt = {
-		.index   = ci->tcf_index,
-		.refcnt  = refcount_read(&ci->tcf_refcnt) - ref,
-		.bindcnt = atomic_read(&ci->tcf_bindcnt) - bind,
-	};
+	struct tc_connmark opt;
 	struct tcf_t t;
 
+	memset(&opt, 0, sizeof(opt));
+
+	opt.index   = ci->tcf_index;
+	opt.refcnt  = refcount_read(&ci->tcf_refcnt) - ref;
+	opt.bindcnt = atomic_read(&ci->tcf_bindcnt) - bind;
+
 	rcu_read_lock();
 	parms = rcu_dereference(ci->parms);
 

-- 
2.43.0