Subject: Re: [PATCH bpf-next 5/8] bpf: Add link-based BPF program attachment to network namespace

From: kbuild test robot <[email-masked]>
Date: Thu, 28 May 2020 10:54:21 +0800

Hi Jakub,

I love your patch! Perhaps something to improve:

[auto build test WARNING on bpf-next/master]
[also build test WARNING on net-next/master next-20200526]
[cannot apply to bpf/master net/master linus/master v5.7-rc7]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Jakub-Sitnicki/Link-based-program-attachment-to-network-namespaces/20200528-011159
base:   https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
config: arm-randconfig-r035-20200527 (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 3393cc4cebf9969db94dc424b7a2b6195589c33b)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <[email-masked]>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> kernel/bpf/net_namespace.c:130:6: warning: variable 'inum' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
if (net)
^~~
kernel/bpf/net_namespace.c:134:26: note: uninitialized use occurs here
info->netns.netns_ino = inum;
^~~~
kernel/bpf/net_namespace.c:130:2: note: remove the 'if' if its condition is always true
if (net)
^~~~~~~~
kernel/bpf/net_namespace.c:123:19: note: initialize the variable 'inum' to silence this warning
unsigned int inum;
^
= 0
1 warning generated.

vim +130 kernel/bpf/net_namespace.c

   118	
   119	static int bpf_netns_link_fill_info(const struct bpf_link *link,
   120					    struct bpf_link_info *info)
   121	{
   122		const struct bpf_netns_link *net_link;
   123		unsigned int inum;
   124		struct net *net;
   125	
   126		net_link = container_of(link, struct bpf_netns_link, link);
   127	
   128		rcu_read_lock();
   129		net = rcu_dereference(net_link->net);
 > 130		if (net)
   131			inum = net->ns.inum;
   132		rcu_read_unlock();
   133	
   134		info->netns.netns_ino = inum;
   135		info->netns.attach_type = net_link->type;
   136		return 0;
   137	}
   138	

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0-DAY CI Kernel Test Service, Intel Corporation
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