net/ipv6/addrconf.c:557 dev_forward_change() error: we previously assumed 'dev' could be null (see line 541)

Hi Nicolas,

FYI, there are new smatch warnings show up in

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git master
head:   a932657f51eadb8280166e82dc7034dfbff3985a
commit: f3a1bfb11ccbc72d44f0b58c92115a40128979c3 [86/92] rtnl/ipv6: use netconf msg to advertise forwarding status

net/ipv6/addrconf.c:394 ipv6_add_dev() warn: 'dev' held on error path.
+ net/ipv6/addrconf.c:557 dev_forward_change() error: we previously assumed 'dev' could be null (see line 541) net/ipv6/addrconf.c:885 ipv6_del_addr() error: potential NULL dereference 'rt'.

vim +557 +/dev net/ipv6/addrconf.c

^1da177e Linus Torvalds    2005-04-16  535  
^1da177e Linus Torvalds    2005-04-16  536  	if (!idev)
^1da177e Linus Torvalds    2005-04-16  537  		return;
^1da177e Linus Torvalds    2005-04-16  538  	dev = idev->dev;
0187bdfb Ben Hutchings     2008-06-19  539  	if (idev->cnf.forwarding)
0187bdfb Ben Hutchings     2008-06-19  540  		dev_disable_lro(dev);
^1da177e Linus Torvalds    2005-04-16 @541  	if (dev && (dev->flags & IFF_MULTICAST)) {
^1da177e Linus Torvalds    2005-04-16  542  		if (idev->cnf.forwarding)
f3ee4010 YOSHIFUJI Hideaki 2008-04-10  543  			ipv6_dev_mc_inc(dev, &in6addr_linklocal_allrouters);
^1da177e Linus Torvalds    2005-04-16  544  		else
f3ee4010 YOSHIFUJI Hideaki 2008-04-10  545  			ipv6_dev_mc_dec(dev, &in6addr_linklocal_allrouters);
^1da177e Linus Torvalds    2005-04-16  546  	}
502a2ffd stephen hemminger 2010-03-17  547  
502a2ffd stephen hemminger 2010-03-17  548  	list_for_each_entry(ifa, &idev->addr_list, if_list) {
2c12a74c Michal Wrobel     2007-02-26  549  		if (ifa->flags&IFA_F_TENTATIVE)
2c12a74c Michal Wrobel     2007-02-26  550  			continue;
^1da177e Linus Torvalds    2005-04-16  551  		if (idev->cnf.forwarding)
^1da177e Linus Torvalds    2005-04-16  552  			addrconf_join_anycast(ifa);
^1da177e Linus Torvalds    2005-04-16  553  		else
^1da177e Linus Torvalds    2005-04-16  554  			addrconf_leave_anycast(ifa);
^1da177e Linus Torvalds    2005-04-16  555  	}
f3a1bfb1 Nicolas Dichtel   2012-10-25  556  	inet6_netconf_notify_devconf(dev_net(dev), NETCONFA_FORWARDING,
f3a1bfb1 Nicolas Dichtel   2012-10-25 @557  				     dev->ifindex, &idev->cnf);
^1da177e Linus Torvalds    2005-04-16  558  }
^1da177e Linus Torvalds    2005-04-16  559  
^1da177e Linus Torvalds    2005-04-16  560  

---
0-DAY kernel build testing backend Open Source Technology Center
Fengguang Wu, Yuanhan Liu Intel Corporation

idev->dev cannot be NULL.

---
 net/ipv6/addrconf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 8f0b12a..c9b1cf3 100644
@@ -607,7 +607,7 @@ static void dev_forward_change(struct inet6_dev *idev)
 	dev = idev->dev;
 	if (idev->cnf.forwarding)
 		dev_disable_lro(dev);
-	if (dev && (dev->flags & IFF_MULTICAST)) {
+	if (dev->flags & IFF_MULTICAST) {
 		if (idev->cnf.forwarding)
 			ipv6_dev_mc_inc(dev, &in6addr_linklocal_allrouters);
 		else

1.7.12

I sent a same patch before you:

http://marc.info/?l=linux-netdev&m=135148225303417&w=2

:)

Yes, and it got proper attribution to Fengguang Wu

Thanks

Please ignore, the patch has already be sent by Cong Wang <[email protected]>.