Re: [PATCH] sched: address a potential NULL pointer dereference in the GRED scheduler.

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

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20250304141858.3392957-2-juny24602@gmail.com>
References: <20250304141858.3392957-2-juny24602@gmail.com>
TO: kwqcheii <juny24602@gmail.com>
TO: netdev@vger.kernel.org
CC: kwqcheii <juny24602@gmail.com>

Hi kwqcheii,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.14-rc5 next-20250306]
[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/kwqcheii/sched-address-a-potential-NULL-pointer-dereference-in-the-GRED-scheduler/20250304-224144
base:   linus/master
patch link:    https://lore.kernel.org/r/20250304141858.3392957-2-juny24602%40gmail.com
patch subject: [PATCH] sched: address a potential NULL pointer dereference in the GRED scheduler.
:::::: branch date: 2 days ago
:::::: commit date: 2 days ago
config: riscv-randconfig-r072-20250306 (https://download.01.org/0day-ci/archive/20250307/202503070956.I8Z06FRE-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)

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>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202503070956.I8Z06FRE-lkp@intel.com/

New smatch warnings:
net/sched/sch_gred.c:330 gred_offload() error: we previously assumed 'opt' could be null (see line 320)

Old smatch warnings:
net/sched/sch_gred.c:474 gred_change_table_def() warn: potential spectre issue 'table->tab' [w]

vim +/opt +330 net/sched/sch_gred.c

^1da177e4c3f41 Linus Torvalds 2005-04-16  310  
890d8d23ec3c9e Jakub Kicinski 2018-11-19  311  static void gred_offload(struct Qdisc *sch, enum tc_gred_command command)
890d8d23ec3c9e Jakub Kicinski 2018-11-19  312  {
890d8d23ec3c9e Jakub Kicinski 2018-11-19  313  	struct gred_sched *table = qdisc_priv(sch);
890d8d23ec3c9e Jakub Kicinski 2018-11-19  314  	struct net_device *dev = qdisc_dev(sch);
f25c0515c52137 Arnd Bergmann  2021-10-26  315  	struct tc_gred_qopt_offload *opt = table->opt;
890d8d23ec3c9e Jakub Kicinski 2018-11-19  316  
890d8d23ec3c9e Jakub Kicinski 2018-11-19  317  	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
890d8d23ec3c9e Jakub Kicinski 2018-11-19  318  		return;
890d8d23ec3c9e Jakub Kicinski 2018-11-19  319  
8eb926feee9101 kwqcheii       2025-03-04 @320  	if (opt) {
f25c0515c52137 Arnd Bergmann  2021-10-26  321  		memset(opt, 0, sizeof(*opt));
f25c0515c52137 Arnd Bergmann  2021-10-26  322  		opt->command = command;
f25c0515c52137 Arnd Bergmann  2021-10-26  323  		opt->handle = sch->handle;
f25c0515c52137 Arnd Bergmann  2021-10-26  324  		opt->parent = sch->parent;
8eb926feee9101 kwqcheii       2025-03-04  325  	}
f25c0515c52137 Arnd Bergmann  2021-10-26  326  
890d8d23ec3c9e Jakub Kicinski 2018-11-19  327  	if (command == TC_GRED_REPLACE) {
890d8d23ec3c9e Jakub Kicinski 2018-11-19  328  		unsigned int i;
890d8d23ec3c9e Jakub Kicinski 2018-11-19  329  
f25c0515c52137 Arnd Bergmann  2021-10-26 @330  		opt->set.grio_on = gred_rio_mode(table);
f25c0515c52137 Arnd Bergmann  2021-10-26  331  		opt->set.wred_on = gred_wred_mode(table);
f25c0515c52137 Arnd Bergmann  2021-10-26  332  		opt->set.dp_cnt = table->DPs;
f25c0515c52137 Arnd Bergmann  2021-10-26  333  		opt->set.dp_def = table->def;
890d8d23ec3c9e Jakub Kicinski 2018-11-19  334  
890d8d23ec3c9e Jakub Kicinski 2018-11-19  335  		for (i = 0; i < table->DPs; i++) {
890d8d23ec3c9e Jakub Kicinski 2018-11-19  336  			struct gred_sched_data *q = table->tab[i];
890d8d23ec3c9e Jakub Kicinski 2018-11-19  337  
890d8d23ec3c9e Jakub Kicinski 2018-11-19  338  			if (!q)
890d8d23ec3c9e Jakub Kicinski 2018-11-19  339  				continue;
f25c0515c52137 Arnd Bergmann  2021-10-26  340  			opt->set.tab[i].present = true;
f25c0515c52137 Arnd Bergmann  2021-10-26  341  			opt->set.tab[i].limit = q->limit;
f25c0515c52137 Arnd Bergmann  2021-10-26  342  			opt->set.tab[i].prio = q->prio;
f25c0515c52137 Arnd Bergmann  2021-10-26  343  			opt->set.tab[i].min = q->parms.qth_min >> q->parms.Wlog;
f25c0515c52137 Arnd Bergmann  2021-10-26  344  			opt->set.tab[i].max = q->parms.qth_max >> q->parms.Wlog;
f25c0515c52137 Arnd Bergmann  2021-10-26  345  			opt->set.tab[i].is_ecn = gred_use_ecn(q);
f25c0515c52137 Arnd Bergmann  2021-10-26  346  			opt->set.tab[i].is_harddrop = gred_use_harddrop(q);
f25c0515c52137 Arnd Bergmann  2021-10-26  347  			opt->set.tab[i].probability = q->parms.max_P;
f25c0515c52137 Arnd Bergmann  2021-10-26  348  			opt->set.tab[i].backlog = &q->backlog;
890d8d23ec3c9e Jakub Kicinski 2018-11-19  349  		}
f25c0515c52137 Arnd Bergmann  2021-10-26  350  		opt->set.qstats = &sch->qstats;
890d8d23ec3c9e Jakub Kicinski 2018-11-19  351  	}
890d8d23ec3c9e Jakub Kicinski 2018-11-19  352  
f25c0515c52137 Arnd Bergmann  2021-10-26  353  	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_GRED, opt);
890d8d23ec3c9e Jakub Kicinski 2018-11-19  354  }
890d8d23ec3c9e Jakub Kicinski 2018-11-19  355  

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