[bug report] devlink: Move devlink dev reload code to dev

[Dan Carpenter <dan.carpenter@linaro.org>]

Hello Moshe Shemesh,

Commit c6ed7d6ef929 ("devlink: Move devlink dev reload code to dev")
from Feb 2, 2023 (linux-next), leads to the following Smatch static
checker warning:

	net/devlink/dev.c:408 devlink_netns_get()
	error: potential NULL/IS_ERR bug 'net'

net/devlink/dev.c
    378 static struct net *devlink_netns_get(struct sk_buff *skb,
    379                                      struct genl_info *info)
    380 {
    381         struct nlattr *netns_pid_attr = info->attrs[DEVLINK_ATTR_NETNS_PID];
    382         struct nlattr *netns_fd_attr = info->attrs[DEVLINK_ATTR_NETNS_FD];
    383         struct nlattr *netns_id_attr = info->attrs[DEVLINK_ATTR_NETNS_ID];
    384         struct net *net;
    385 
    386         if (!!netns_pid_attr + !!netns_fd_attr + !!netns_id_attr > 1) {
    387                 NL_SET_ERR_MSG(info->extack, "multiple netns identifying attributes specified");
    388                 return ERR_PTR(-EINVAL);
    389         }
    390 
    391         if (netns_pid_attr) {
    392                 net = get_net_ns_by_pid(nla_get_u32(netns_pid_attr));

Smatch thinks that the "net = get_net(nsproxy->net_ns);" could mean that
get_net_ns_by_pid() returns NULL.  I don't know if that's correct or not.
If someone could tell me, then it's easy for me to add a line
"get_net_ns_by_pid 0" to the smatch_data/db/kernel.delete.return_states
file but I'd prefer to be sure before I do that...

    393         } else if (netns_fd_attr) {
    394                 net = get_net_ns_by_fd(nla_get_u32(netns_fd_attr));
    395         } else if (netns_id_attr) {
    396                 net = get_net_ns_by_id(sock_net(skb->sk),
    397                                        nla_get_u32(netns_id_attr));
    398                 if (!net)
    399                         net = ERR_PTR(-EINVAL);
    400         } else {
    401                 WARN_ON(1);
    402                 net = ERR_PTR(-EINVAL);
    403         }
    404         if (IS_ERR(net)) {
    405                 NL_SET_ERR_MSG(info->extack, "Unknown network namespace");
    406                 return ERR_PTR(-EINVAL);
    407         }
--> 408         if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN)) {
    409                 put_net(net);
    410                 return ERR_PTR(-EPERM);
    411         }
    412         return net;
    413 }

regards,
dan carpenter