kernel-janitors.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [bug report] rtnetlink: Return correct error on changing device netns
@ 2021-08-30  9:04 Dan Carpenter
  2021-08-31  7:06 ` Andrey Ignatov
  0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2021-08-30  9:04 UTC (permalink / raw)
  To: rdna; +Cc: kernel-janitors

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

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [bug report] rtnetlink: Return correct error on changing device netns
  2021-08-30  9:04 [bug report] rtnetlink: Return correct error on changing device netns Dan Carpenter
@ 2021-08-31  7:06 ` Andrey Ignatov
  2021-08-31  9:03   ` Dan Carpenter
  0 siblings, 1 reply; 3+ messages in thread
From: Andrey Ignatov @ 2021-08-31  7:06 UTC (permalink / raw)
  To: Dan Carpenter; +Cc: kernel-janitors, Jakub Kicinski

Dan Carpenter <dan.carpenter@oracle.com> [Mon, 2021-08-30 02:04 -0700]:
> 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?

Yes. There is one do_setlink() call that passes NULL as ifname:

net/core/rtnetlink.c

static int rtnl_group_changelink(const struct sk_buff *skb,
...
			err = do_setlink(skb, dev, ifm, extack, tb, NULL, 0);

It handles IFLA_GROUP that can be used with these netns attributes.

W/o the NULL check something like `ip link set group GROUP netns NETNS`
would cause a panic like this:

# ./ifname.sh
+ ip netns add ns0
+ ip link add g1 group 1 type dummy
+ ip link show group 1
10: g1: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN mode DEFAULT group 1 qlen 1000
    link/ether ba:3c:5e:9d:8e:ab brd ff:ff:ff:ff:ff:ff
+ ip link set group 1 netns ns0
[    7.566918] BUG: kernel NULL pointer dereference, address: 0000000000000000
[    7.567746] #PF: supervisor read access in kernel mode
[    7.568299] #PF: error_code(0x0000) - not-present page
[    7.568853] PGD 8000000107758067 P4D 8000000107758067 PUD 107757067 PMD 0
[    7.569638] Oops: 0000 [#1] SMP PTI
[    7.570007] CPU: 2 PID: 242 Comm: ip Not tainted 5.14.0-rc7-00093-g1a6436f37512-dirty #533
[    7.570918] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
[    7.572126] RIP: 0010:do_setlink+0x69/0x1070
...

>   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		}
...
>   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.

+Jakub

As Jakub explained in [0] this code can not be called with ifname=NULL
because the only do_setlink() call with ifname=NULL is done only when
`ifm->ifi_index == 0` so it looks like false positive.

[0]
https://lore.kernel.org/netdev/20210830094301.4f6ada72@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com/


-- 
Andrey Ignatov

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [bug report] rtnetlink: Return correct error on changing device netns
  2021-08-31  7:06 ` Andrey Ignatov
@ 2021-08-31  9:03   ` Dan Carpenter
  0 siblings, 0 replies; 3+ messages in thread
From: Dan Carpenter @ 2021-08-31  9:03 UTC (permalink / raw)
  To: Andrey Ignatov; +Cc: kernel-janitors, Jakub Kicinski

Thanks.  In theory, Smatch is supposed to be able to parse this
correctly but do_setlink() is too complicated for Smatch.

net/core/rtnetlink.c:2824 do_setlink() warn: Function too hairy.  No more merges.

So then the callers think that ifm->ifi_index is not used and they don't
pass that information.  It's hard to know how to fix this...

regards,
dan carpenter


^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-08-31  9:03 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-30  9:04 [bug report] rtnetlink: Return correct error on changing device netns Dan Carpenter
2021-08-31  7:06 ` Andrey Ignatov
2021-08-31  9:03   ` Dan Carpenter

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).