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Date: Mon, 1 Jan 2024 08:54:14 +0800
From: kernel test robot <lkp@intel.com>
To: Markus Elfring <Markus.Elfring@web.de>, netdev@vger.kernel.org,
	kernel-janitors@vger.kernel.org,
	Anjali Kulkarni <anjali.k.kulkarni@oracle.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Kuniyuki Iwashima <kuniyu@amazon.com>,
	Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>
Cc: llvm@lists.linux.dev, oe-kbuild-all@lists.linux.dev,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/4] netlink: Move =?utf-8?Q?an?=
 =?utf-8?Q?_assignment_for_the_variable_=E2=80=9Csk?= =?utf-8?B?4oCd?= in
 __netlink_kernel_create()
Message-ID: <202401010855.4iU6im1B-lkp@intel.com>
References: <223a61e9-f826-4f37-b514-ca6ed53b1269@web.de>
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In-Reply-To: <223a61e9-f826-4f37-b514-ca6ed53b1269@web.de>

Hi Markus,

kernel test robot noticed the following build warnings:

[auto build test WARNING on net/main]
[also build test WARNING on net-next/main linus/master horms-ipvs/master v6.7-rc8 next-20231222]
[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/Markus-Elfring/netlink-Improve-exception-handling-in-__netlink_kernel_create/20240101-015025
base:   net/main
patch link:    https://lore.kernel.org/r/223a61e9-f826-4f37-b514-ca6ed53b1269%40web.de
patch subject: [PATCH 2/4] netlink: Move an assignment for the variable “sk” in __netlink_kernel_create()
config: arm-randconfig-001-20240101 (https://download.01.org/0day-ci/archive/20240101/202401010855.4iU6im1B-lkp@intel.com/config)
compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project 8a4266a626914765c0c69839e8a51be383013c1a)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240101/202401010855.4iU6im1B-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/202401010855.4iU6im1B-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> net/netlink/af_netlink.c:2044:6: warning: variable 'sk' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
    2044 |         if (!listeners)
         |             ^~~~~~~~~~
   net/netlink/af_netlink.c:2081:25: note: uninitialized use occurs here
    2081 |         netlink_kernel_release(sk);
         |                                ^~
   net/netlink/af_netlink.c:2044:2: note: remove the 'if' if its condition is always false
    2044 |         if (!listeners)
         |         ^~~~~~~~~~~~~~~
    2045 |                 goto out_netlink_release_sock;
         |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   net/netlink/af_netlink.c:2021:17: note: initialize the variable 'sk' to silence this warning
    2021 |         struct sock *sk;
         |                        ^
         |                         = NULL
   1 warning generated.


vim +2044 net/netlink/af_netlink.c

^1da177e4c3f41 Linus Torvalds    2005-04-16  2009  
^1da177e4c3f41 Linus Torvalds    2005-04-16  2010  /*
^1da177e4c3f41 Linus Torvalds    2005-04-16  2011   *	We export these functions to other modules. They provide a
^1da177e4c3f41 Linus Torvalds    2005-04-16  2012   *	complete set of kernel non-blocking support for message
^1da177e4c3f41 Linus Torvalds    2005-04-16  2013   *	queueing.
^1da177e4c3f41 Linus Torvalds    2005-04-16  2014   */
^1da177e4c3f41 Linus Torvalds    2005-04-16  2015  
^1da177e4c3f41 Linus Torvalds    2005-04-16  2016  struct sock *
9f00d9776bc5be Pablo Neira Ayuso 2012-09-08  2017  __netlink_kernel_create(struct net *net, int unit, struct module *module,
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2018  			struct netlink_kernel_cfg *cfg)
^1da177e4c3f41 Linus Torvalds    2005-04-16  2019  {
^1da177e4c3f41 Linus Torvalds    2005-04-16  2020  	struct socket *sock;
^1da177e4c3f41 Linus Torvalds    2005-04-16  2021  	struct sock *sk;
77247bbb309424 Patrick McHardy   2005-08-14  2022  	struct netlink_sock *nlk;
5c398dc8f5a58b Eric Dumazet      2010-10-24  2023  	struct listeners *listeners = NULL;
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2024  	struct mutex *cb_mutex = cfg ? cfg->cb_mutex : NULL;
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2025  	unsigned int groups;
^1da177e4c3f41 Linus Torvalds    2005-04-16  2026  
fab2caf62ed03d Akinobu Mita      2006-08-29  2027  	BUG_ON(!nl_table);
^1da177e4c3f41 Linus Torvalds    2005-04-16  2028  
^1da177e4c3f41 Linus Torvalds    2005-04-16  2029  	if (unit < 0 || unit >= MAX_LINKS)
^1da177e4c3f41 Linus Torvalds    2005-04-16  2030  		return NULL;
^1da177e4c3f41 Linus Torvalds    2005-04-16  2031  
^1da177e4c3f41 Linus Torvalds    2005-04-16  2032  	if (sock_create_lite(PF_NETLINK, SOCK_DGRAM, unit, &sock))
^1da177e4c3f41 Linus Torvalds    2005-04-16  2033  		return NULL;
13d3078e22f565 Eric W. Biederman 2015-05-08  2034  
13d3078e22f565 Eric W. Biederman 2015-05-08  2035  	if (__netlink_create(net, sock, cb_mutex, unit, 1) < 0)
23fe18669e7fda Pavel Emelyanov   2008-01-30  2036  		goto out_sock_release_nosk;
23fe18669e7fda Pavel Emelyanov   2008-01-30  2037  
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2038  	if (!cfg || cfg->groups < 32)
4277a083ecd2c8 Patrick McHardy   2006-03-20  2039  		groups = 32;
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2040  	else
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2041  		groups = cfg->groups;
4277a083ecd2c8 Patrick McHardy   2006-03-20  2042  
5c398dc8f5a58b Eric Dumazet      2010-10-24  2043  	listeners = kzalloc(sizeof(*listeners) + NLGRPSZ(groups), GFP_KERNEL);
4277a083ecd2c8 Patrick McHardy   2006-03-20 @2044  	if (!listeners)
90ae404765d263 Markus Elfring    2023-12-31  2045  		goto out_netlink_release_sock;
4277a083ecd2c8 Patrick McHardy   2006-03-20  2046  
e547df909ec09d Markus Elfring    2023-12-31  2047  	sk = sock->sk;
^1da177e4c3f41 Linus Torvalds    2005-04-16  2048  	sk->sk_data_ready = netlink_data_ready;
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2049  	if (cfg && cfg->input)
a31f2d17b331db Pablo Neira Ayuso 2012-06-29  2050  		nlk_sk(sk)->netlink_rcv = cfg->input;
^1da177e4c3f41 Linus Torvalds    2005-04-16  2051  
8ea65f4a2dfaaf Herbert Xu        2015-01-26  2052  	if (netlink_insert(sk, 0))
77247bbb309424 Patrick McHardy   2005-08-14  2053  		goto out_sock_release;
4fdb3bb723db46 Harald Welte      2005-08-09  2054  
77247bbb309424 Patrick McHardy   2005-08-14  2055  	nlk = nlk_sk(sk);
8fe08d70a2b61b Eric Dumazet      2023-08-11  2056  	set_bit(NETLINK_F_KERNEL_SOCKET, &nlk->flags);
4fdb3bb723db46 Harald Welte      2005-08-09  2057  
4fdb3bb723db46 Harald Welte      2005-08-09  2058  	netlink_table_grab();
b4b510290b056b Eric W. Biederman 2007-09-12  2059  	if (!nl_table[unit].registered) {
4277a083ecd2c8 Patrick McHardy   2006-03-20  2060  		nl_table[unit].groups = groups;
5c398dc8f5a58b Eric Dumazet      2010-10-24  2061  		rcu_assign_pointer(nl_table[unit].listeners, listeners);
af65bdfce98d79 Patrick McHardy   2007-04-20  2062  		nl_table[unit].cb_mutex = cb_mutex;
77247bbb309424 Patrick McHardy   2005-08-14  2063  		nl_table[unit].module = module;
9785e10aedfa0f Pablo Neira Ayuso 2012-09-08  2064  		if (cfg) {
9785e10aedfa0f Pablo Neira Ayuso 2012-09-08  2065  			nl_table[unit].bind = cfg->bind;
6251edd932ce3f Hiroaki SHIMODA   2014-11-13  2066  			nl_table[unit].unbind = cfg->unbind;
a4c9a56e6a2cde Anjali Kulkarni   2023-07-19  2067  			nl_table[unit].release = cfg->release;
9785e10aedfa0f Pablo Neira Ayuso 2012-09-08  2068  			nl_table[unit].flags = cfg->flags;
9785e10aedfa0f Pablo Neira Ayuso 2012-09-08  2069  		}
ab33a1711cf60b Patrick McHardy   2005-08-14  2070  		nl_table[unit].registered = 1;
f937f1f46b6d2f Jesper Juhl       2007-10-15  2071  	} else {
f937f1f46b6d2f Jesper Juhl       2007-10-15  2072  		kfree(listeners);
869e58f87094b1 Denis V. Lunev    2008-01-18  2073  		nl_table[unit].registered++;
b4b510290b056b Eric W. Biederman 2007-09-12  2074  	}
4fdb3bb723db46 Harald Welte      2005-08-09  2075  	netlink_table_ungrab();
77247bbb309424 Patrick McHardy   2005-08-14  2076  	return sk;
77247bbb309424 Patrick McHardy   2005-08-14  2077  
4fdb3bb723db46 Harald Welte      2005-08-09  2078  out_sock_release:
4277a083ecd2c8 Patrick McHardy   2006-03-20  2079  	kfree(listeners);
90ae404765d263 Markus Elfring    2023-12-31  2080  out_netlink_release_sock:
9dfbec1fb2bedf Denis V. Lunev    2008-02-29  2081  	netlink_kernel_release(sk);
23fe18669e7fda Pavel Emelyanov   2008-01-30  2082  	return NULL;
23fe18669e7fda Pavel Emelyanov   2008-01-30  2083  
23fe18669e7fda Pavel Emelyanov   2008-01-30  2084  out_sock_release_nosk:
4fdb3bb723db46 Harald Welte      2005-08-09  2085  	sock_release(sock);
77247bbb309424 Patrick McHardy   2005-08-14  2086  	return NULL;
^1da177e4c3f41 Linus Torvalds    2005-04-16  2087  }
9f00d9776bc5be Pablo Neira Ayuso 2012-09-08  2088  EXPORT_SYMBOL(__netlink_kernel_create);
b7c6ba6eb1234e Denis V. Lunev    2008-01-28  2089  

-- 
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https://github.com/intel/lkp-tests/wiki