[PATCH 5.17 169/298] amt: fix possible null-ptr-deref in amt_rcv()

From: Greg Kroah-Hartman
Date: Mon Jun 13 2022 - 10:34:49 EST


From: Taehee Yoo <ap420073@xxxxxxxxx>

[ Upstream commit d16207f92a4a823c48b4ea953ad51f4483456768 ]

When amt interface receives amt message, it tries to obtain amt private
data from sock.
If there is no amt private data, it frees an skb immediately.
After kfree_skb(), it increases the rx_dropped stats.
But in order to use rx_dropped, amt private data is needed.
So, it makes amt_rcv() to do not increase rx_dropped stats when it can
not obtain amt private data.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Fixes: 1a1a0e80e005 ("amt: fix possible memory leak in amt_rcv()")
Signed-off-by: Taehee Yoo <ap420073@xxxxxxxxx>
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/net/amt.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/amt.c b/drivers/net/amt.c
index d8c47c4e6559..e239c0262d56 100644
--- a/drivers/net/amt.c
+++ b/drivers/net/amt.c
@@ -2698,7 +2698,8 @@ static int amt_rcv(struct sock *sk, struct sk_buff *skb)
amt = rcu_dereference_sk_user_data(sk);
if (!amt) {
err = true;
- goto drop;
+ kfree_skb(skb);
+ goto out;
}

skb->dev = amt->dev;
--
2.35.1