[PATCH] netfilter: nf_tables: fix use-after-free on ops->dev

[Helen Koike <koike@igalia.com>]

struct nf_hook_ops has a pointer to dev, which can be used by
__nf_unregister_net_hook() after it has been freed by tun_chr_close().

Fix it  by calling dev_hold() when saving dev to ops struct.

Reported-by: syzbot+bb9127e278fa198e110c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=bb9127e278fa198e110c
Signed-off-by: Helen Koike <koike@igalia.com>
---
 net/netfilter/nf_tables_api.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index fd7f7e4e2a43..00b5f900a51d 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -352,6 +352,7 @@ static void nft_netdev_hook_free_ops(struct nft_hook *hook)
 
 	list_for_each_entry_safe(ops, next, &hook->ops_list, list) {
 		list_del(&ops->list);
+		dev_put(ops->dev);
 		kfree(ops);
 	}
 }
@@ -2374,6 +2375,7 @@ static struct nft_hook *nft_netdev_hook_alloc(struct net *net,
 			err = -ENOMEM;
 			goto err_hook_free;
 		}
+		dev_hold(dev);
 		ops->dev = dev;
 		list_add_tail(&ops->list, &hook->ops_list);
 	}
-- 
2.53.0