Re: [PATCH] net: Add locking to protect skb->dev access in ip_output

[kernel test robot <lkp@intel.com>]

Hi Sharath,

kernel test robot noticed the following build errors:

[auto build test ERROR on net-next/main]
[also build test ERROR on next-20250723]
[cannot apply to net/main linus/master horms-ipvs/master v6.16-rc7]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Sharath-Chandra-Vurukala/net-Add-locking-to-protect-skb-dev-access-in-ip_output/20250723-162406
base:   net-next/main
patch link:    https://lore.kernel.org/r/20250723082201.GA14090%40hu-sharathv-hyd.qualcomm.com
patch subject: [PATCH] net: Add locking to protect skb->dev access in ip_output
config: i386-randconfig-003-20250724 (https://download.01.org/0day-ci/archive/20250724/202507240835.DPHAwhlJ-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250724/202507240835.DPHAwhlJ-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507240835.DPHAwhlJ-lkp@intel.com/

All errors (new ones prefixed by >>):

   net/ipv4/ip_output.c: In function 'ip_output':
>> net/ipv4/ip_output.c:438:9: error: 'ret_val' undeclared (first use in this function); did you mean 'pte_val'?
     438 |         ret_val = NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
         |         ^~~~~~~
         |         pte_val
   net/ipv4/ip_output.c:438:9: note: each undeclared identifier is reported only once for each function it appears in
   net/ipv4/ip_output.c:444:1: warning: control reaches end of non-void function [-Wreturn-type]
     444 | }
         | ^


vim +438 net/ipv4/ip_output.c

   425	
   426	int ip_output(struct net *net, struct sock *sk, struct sk_buff *skb)
   427	{
   428		struct net_device *dev, *indev = skb->dev;
   429	
   430		IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);
   431	
   432		rcu_read_lock();
   433	
   434		dev = skb_dst(skb)->dev;
   435		skb->dev = dev;
   436		skb->protocol = htons(ETH_P_IP);
   437	
 > 438		ret_val = NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
   439				       net, sk, skb, indev, dev,
   440					ip_finish_output,
   441					!(IPCB(skb)->flags & IPSKB_REROUTED));
   442		rcu_read_unlock();
   443		return ret_val;
   444	}
   445	EXPORT_SYMBOL(ip_output);
   446	

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