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

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Message-ID: <CAKwvOdmof_tGVAN+gkq8R3Hq_sRDHXE_cB+37Sd7gKvgzVzVHw@mail.gmail.com>
Date:   Thu, 4 Jun 2020 16:38:44 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Jakub Sitnicki <jakub@...udflare.com>
Cc:     bpf <bpf@...r.kernel.org>, kbuild-all@...ts.01.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Network Development <netdev@...r.kernel.org>,
        kernel-team@...udflare.com, kbuild test robot <lkp@...el.com>
Subject: Re: [PATCH bpf-next 5/8] bpf: Add link-based BPF program attachment
 to network namespace

On Wed, May 27, 2020 at 8:19 PM kbuild test robot <lkp@...el.com> wrote:
>
> 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 <lkp@...el.com>
>
> 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]

This looks legit to me. Please fix.

> 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
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>
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-- 
Thanks,
~Nick Desaulniers