[bug report] rtnetlink: Return correct error on changing device netns

From: Dan Carpenter <dan.carpenter@oracle.com>
To: rdna@fb.com
Cc: kernel-janitors@vger.kernel.org
Subject: [bug report] rtnetlink: Return correct error on changing device netns
Date: Mon, 30 Aug 2021 12:04:06 +0300	[thread overview]
Message-ID: <20210830090405.GA6314@kili> (raw)

Hello Andrey Ignatov,

This is a semi-automatic email about new static checker warnings.

The patch 96a6b93b6988: "rtnetlink: Return correct error on changing
device netns" from Aug 25, 2021, leads to the following Smatch
complaint:

    net/core/rtnetlink.c:2698 do_setlink()
    error: we previously assumed 'ifname' could be null (see line 2608)

net/core/rtnetlink.c
  2607		if (tb[IFLA_NET_NS_PID] || tb[IFLA_NET_NS_FD] || tb[IFLA_TARGET_NETNSID]) {
  2608			const char *pat = ifname && ifname[0] ? ifname : NULL;
                                          ^^^^^^
The patch adds a new check for if "ifname" is NULL.  Is this required?

  2609			struct net *net;
  2610			int new_ifindex;
  2611	
  2612			net = rtnl_link_get_net_capable(skb, dev_net(dev),
  2613							tb, CAP_NET_ADMIN);
  2614			if (IS_ERR(net)) {
  2615				err = PTR_ERR(net);
  2616				goto errout;
  2617			}
  2618	
  2619			if (tb[IFLA_NEW_IFINDEX])
  2620				new_ifindex = nla_get_s32(tb[IFLA_NEW_IFINDEX]);
  2621			else
  2622				new_ifindex = 0;
  2623	
  2624			err = __dev_change_net_namespace(dev, net, pat, new_ifindex);
  2625			put_net(net);
  2626			if (err)
  2627				goto errout;
  2628			status |= DO_SETLINK_MODIFIED;
  2629		}
  2630	
  2631		if (tb[IFLA_MAP]) {
  2632			struct rtnl_link_ifmap *u_map;
  2633			struct ifmap k_map;
  2634	
  2635			if (!ops->ndo_set_config) {
  2636				err = -EOPNOTSUPP;
  2637				goto errout;
  2638			}
  2639	
  2640			if (!netif_device_present(dev)) {
  2641				err = -ENODEV;
  2642				goto errout;
  2643			}
  2644	
  2645			u_map = nla_data(tb[IFLA_MAP]);
  2646			k_map.mem_start = (unsigned long) u_map->mem_start;
  2647			k_map.mem_end = (unsigned long) u_map->mem_end;
  2648			k_map.base_addr = (unsigned short) u_map->base_addr;
  2649			k_map.irq = (unsigned char) u_map->irq;
  2650			k_map.dma = (unsigned char) u_map->dma;
  2651			k_map.port = (unsigned char) u_map->port;
  2652	
  2653			err = ops->ndo_set_config(dev, &k_map);
  2654			if (err < 0)
  2655				goto errout;
  2656	
  2657			status |= DO_SETLINK_NOTIFY;
  2658		}
  2659	
  2660		if (tb[IFLA_ADDRESS]) {
  2661			struct sockaddr *sa;
  2662			int len;
  2663	
  2664			len = sizeof(sa_family_t) + max_t(size_t, dev->addr_len,
  2665							  sizeof(*sa));
  2666			sa = kmalloc(len, GFP_KERNEL);
  2667			if (!sa) {
  2668				err = -ENOMEM;
  2669				goto errout;
  2670			}
  2671			sa->sa_family = dev->type;
  2672			memcpy(sa->sa_data, nla_data(tb[IFLA_ADDRESS]),
  2673			       dev->addr_len);
  2674			err = dev_set_mac_address_user(dev, sa, extack);
  2675			kfree(sa);
  2676			if (err)
  2677				goto errout;
  2678			status |= DO_SETLINK_MODIFIED;
  2679		}
  2680	
  2681		if (tb[IFLA_MTU]) {
  2682			err = dev_set_mtu_ext(dev, nla_get_u32(tb[IFLA_MTU]), extack);
  2683			if (err < 0)
  2684				goto errout;
  2685			status |= DO_SETLINK_MODIFIED;
  2686		}
  2687	
  2688		if (tb[IFLA_GROUP]) {
  2689			dev_set_group(dev, nla_get_u32(tb[IFLA_GROUP]));
  2690			status |= DO_SETLINK_NOTIFY;
  2691		}
  2692	
  2693		/*
  2694		 * Interface selected by interface index but interface
  2695		 * name provided implies that a name change has been
  2696		 * requested.
  2697		 */
  2698		if (ifm->ifi_index > 0 && ifname[0]) {
                                          ^^^^^^^^^
The existing code does not check.

  2699			err = dev_change_name(dev, ifname);
  2700			if (err < 0)

regards,
dan carpenter