linux-kernel - net/dsa/tag_8021q.c:109 dsa_8021q_restore_pvid() error: uninitialized symbol 'pvid'.

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Date:   Tue, 26 May 2020 17:54:54 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     kbuild@...ts.01.org, Vladimir Oltean <olteanv@...il.com>
Cc:     lkp@...el.com, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>
Subject: net/dsa/tag_8021q.c:109 dsa_8021q_restore_pvid() error:
 uninitialized symbol 'pvid'.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   9cb1fd0efd195590b828b9b865421ad345a4a145
commit: c80ed84e76886487703bf04b38ce10e92e2d6e26 net: dsa: tag_8021q: Fix dsa_8021q_restore_pvid for an absent pvid
date:   6 months ago
config: x86_64-randconfig-m001-20200526 (attached as .config)
compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <lkp@...el.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>

smatch warnings:
net/dsa/tag_8021q.c:109 dsa_8021q_restore_pvid() error: uninitialized symbol 'pvid'.

# https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c80ed84e76886487703bf04b38ce10e92e2d6e26
git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
git remote update linus
git checkout c80ed84e76886487703bf04b38ce10e92e2d6e26
vim +/pvid +109 net/dsa/tag_8021q.c

5f33183b7fdfeb Vladimir Oltean 2019-08-30   96  static int dsa_8021q_restore_pvid(struct dsa_switch *ds, int port)
5f33183b7fdfeb Vladimir Oltean 2019-08-30   97  {
5f33183b7fdfeb Vladimir Oltean 2019-08-30   98  	struct bridge_vlan_info vinfo;
5f33183b7fdfeb Vladimir Oltean 2019-08-30   99  	struct net_device *slave;
5f33183b7fdfeb Vladimir Oltean 2019-08-30  100  	u16 pvid;
5f33183b7fdfeb Vladimir Oltean 2019-08-30  101  	int err;
5f33183b7fdfeb Vladimir Oltean 2019-08-30  102  
5f33183b7fdfeb Vladimir Oltean 2019-08-30  103  	if (!dsa_is_user_port(ds, port))
5f33183b7fdfeb Vladimir Oltean 2019-08-30  104  		return 0;
5f33183b7fdfeb Vladimir Oltean 2019-08-30  105  
5f33183b7fdfeb Vladimir Oltean 2019-08-30  106  	slave = ds->ports[port].slave;
5f33183b7fdfeb Vladimir Oltean 2019-08-30  107  
5f33183b7fdfeb Vladimir Oltean 2019-08-30  108  	err = br_vlan_get_pvid(slave, &pvid);
c80ed84e768864 Vladimir Oltean 2019-11-16 @109  	if (!pvid || err < 0)
                                                            ^^^^^^^^^^^^^^^^
I don't know why this warning is only showing up now in May 2020...
Anyway, we could solve the problem by checking for errors first:

	if (err < 0 || !pvid) {

The UBSan tool can detect uninitialized values used at runtime so it
might generate a splat as well.  Other than that, obviously it is
harmless.

5f33183b7fdfeb Vladimir Oltean 2019-08-30  110  		/* There is no pvid on the bridge for this port, which is
5f33183b7fdfeb Vladimir Oltean 2019-08-30  111  		 * perfectly valid. Nothing to restore, bye-bye!
5f33183b7fdfeb Vladimir Oltean 2019-08-30  112  		 */
5f33183b7fdfeb Vladimir Oltean 2019-08-30  113  		return 0;
5f33183b7fdfeb Vladimir Oltean 2019-08-30  114  
5f33183b7fdfeb Vladimir Oltean 2019-08-30  115  	err = br_vlan_get_info(slave, pvid, &vinfo);
5f33183b7fdfeb Vladimir Oltean 2019-08-30  116  	if (err < 0) {
5f33183b7fdfeb Vladimir Oltean 2019-08-30  117  		dev_err(ds->dev, "Couldn't determine PVID attributes\n");
5f33183b7fdfeb Vladimir Oltean 2019-08-30  118  		return err;
5f33183b7fdfeb Vladimir Oltean 2019-08-30  119  	}
5f33183b7fdfeb Vladimir Oltean 2019-08-30  120  
5f33183b7fdfeb Vladimir Oltean 2019-08-30  121  	return dsa_port_vid_add(&ds->ports[port], pvid, vinfo.flags);
5f33183b7fdfeb Vladimir Oltean 2019-08-30  122  }

---
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