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* [peterz-queue:sched/core 13/19] kernel/sched/debug.c:453 print_cfs_group_stats() warn: variable dereferenced before check 'se' (see line 444)
@ 2021-09-13  8:47 Dan Carpenter
  2021-09-13 11:04 ` Yafang Shao
  0 siblings, 1 reply; 3+ messages in thread
From: Dan Carpenter @ 2021-09-13  8:47 UTC (permalink / raw)
  To: kbuild, Yafang Shao; +Cc: lkp, kbuild-all, linux-kernel, Peter Zijlstra

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core
head:   2dfdb3d20ad50e2ae2cb84cbceb0f0fc75e79e5d
commit: 445d9e8ba05d5e9e4b26956b7fe529223e29d8d1 [13/19] sched: make struct sched_statistics independent of fair sched class
config: x86_64-randconfig-m001-20210910 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

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

smatch warnings:
kernel/sched/debug.c:453 print_cfs_group_stats() warn: variable dereferenced before check 'se' (see line 444)

vim +/se +453 kernel/sched/debug.c

3866e845ed5222 kernel/sched/debug.c Steven Rostedt (Red Hat  2016-02-22  439) 
ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  440  #ifdef CONFIG_FAIR_GROUP_SCHED
5091faa449ee0b kernel/sched_debug.c Mike Galbraith           2010-11-30  441  static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group *tg)
ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  442  {
ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  443  	struct sched_entity *se = tg->se[cpu];
445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05 @444  	struct sched_statistics *stats = __schedstats_from_se(se);
                                                                                                                                      ^^
New unchecked dereference.

ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  445  
97fb7a0a8944bd kernel/sched/debug.c Ingo Molnar              2018-03-03  446  #define P(F)		SEQ_printf(m, "  .%-30s: %lld\n",	#F, (long long)F)
445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  447  #define P_SCHEDSTAT(F)	SEQ_printf(m, "  .%-30s: %lld\n",	\
445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  448  		#F, (long long)schedstat_val(stats->F))
97fb7a0a8944bd kernel/sched/debug.c Ingo Molnar              2018-03-03  449  #define PN(F)		SEQ_printf(m, "  .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)F))
445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  450  #define PN_SCHEDSTAT(F)	SEQ_printf(m, "  .%-30s: %lld.%06ld\n", \
445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  451  		#F, SPLIT_NS((long long)schedstat_val(stats->F)))
ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  452  
cd126afe838d7e kernel/sched/debug.c Yuyang Du                2015-07-15 @453  	if (!se)
                                                                                    ^^^
The old code assumed "se" can be NULL.

18bf2805d9b30c kernel/sched/debug.c Ben Segall               2012-10-04  454  		return;
18bf2805d9b30c kernel/sched/debug.c Ben Segall               2012-10-04  455  
ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  456  	PN(se->exec_start);
ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  457  	PN(se->vruntime);

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


^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [peterz-queue:sched/core 13/19] kernel/sched/debug.c:453 print_cfs_group_stats() warn: variable dereferenced before check 'se' (see line 444)
  2021-09-13  8:47 [peterz-queue:sched/core 13/19] kernel/sched/debug.c:453 print_cfs_group_stats() warn: variable dereferenced before check 'se' (see line 444) Dan Carpenter
@ 2021-09-13 11:04 ` Yafang Shao
  2021-09-13 12:02   ` Peter Zijlstra
  0 siblings, 1 reply; 3+ messages in thread
From: Yafang Shao @ 2021-09-13 11:04 UTC (permalink / raw)
  To: Dan Carpenter; +Cc: kbuild, kbuild test robot, kbuild-all, LKML, Peter Zijlstra

On Mon, Sep 13, 2021 at 4:48 PM Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/core
> head:   2dfdb3d20ad50e2ae2cb84cbceb0f0fc75e79e5d
> commit: 445d9e8ba05d5e9e4b26956b7fe529223e29d8d1 [13/19] sched: make struct sched_statistics independent of fair sched class
> config: x86_64-randconfig-m001-20210910 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
>
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> smatch warnings:
> kernel/sched/debug.c:453 print_cfs_group_stats() warn: variable dereferenced before check 'se' (see line 444)
>

Sorry, my bad.

Hi Peter,

Could you pls. help amend below change to the original commit ?

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 52b4426414c0..d59f33ac06fe 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -440,11 +440,8 @@ void dirty_sched_domain_sysctl(int cpu)
 #ifdef CONFIG_FAIR_GROUP_SCHED
 static void print_cfs_group_stats(struct seq_file *m, int cpu, struct
task_group *tg)
 {
-       struct sched_statistics __maybe_unused *stats;
        struct sched_entity *se = tg->se[cpu];

-       stats = __schedstats_from_se(se);
-
 #define P(F)           SEQ_printf(m, "  .%-30s: %lld\n",       #F,
(long long)F)
 #define P_SCHEDSTAT(F) SEQ_printf(m, "  .%-30s: %lld\n",       \
                #F, (long long)schedstat_val(stats->F))
@@ -460,6 +457,8 @@ static void print_cfs_group_stats(struct seq_file
*m, int cpu, struct task_group
        PN(se->sum_exec_runtime);

        if (schedstat_enabled()) {
+               struct sched_statistics *stats =  __schedstats_from_se(se);
+
                PN_SCHEDSTAT(wait_start);
                PN_SCHEDSTAT(sleep_start);
                PN_SCHEDSTAT(block_start);



> vim +/se +453 kernel/sched/debug.c
>
> 3866e845ed5222 kernel/sched/debug.c Steven Rostedt (Red Hat  2016-02-22  439)
> ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  440  #ifdef CONFIG_FAIR_GROUP_SCHED
> 5091faa449ee0b kernel/sched_debug.c Mike Galbraith           2010-11-30  441  static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group *tg)
> ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  442  {
> ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  443    struct sched_entity *se = tg->se[cpu];
> 445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05 @444    struct sched_statistics *stats = __schedstats_from_se(se);
>                                                                                                                                       ^^
> New unchecked dereference.
>
> ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  445
> 97fb7a0a8944bd kernel/sched/debug.c Ingo Molnar              2018-03-03  446  #define P(F)              SEQ_printf(m, "  .%-30s: %lld\n",       #F, (long long)F)
> 445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  447  #define P_SCHEDSTAT(F)    SEQ_printf(m, "  .%-30s: %lld\n",       \
> 445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  448            #F, (long long)schedstat_val(stats->F))
> 97fb7a0a8944bd kernel/sched/debug.c Ingo Molnar              2018-03-03  449  #define PN(F)             SEQ_printf(m, "  .%-30s: %lld.%06ld\n", #F, SPLIT_NS((long long)F))
> 445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  450  #define PN_SCHEDSTAT(F)   SEQ_printf(m, "  .%-30s: %lld.%06ld\n", \
> 445d9e8ba05d5e kernel/sched/debug.c Yafang Shao              2021-09-05  451            #F, SPLIT_NS((long long)schedstat_val(stats->F)))
> ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  452
> cd126afe838d7e kernel/sched/debug.c Yuyang Du                2015-07-15 @453    if (!se)
>                                                                                     ^^^
> The old code assumed "se" can be NULL.
>
> 18bf2805d9b30c kernel/sched/debug.c Ben Segall               2012-10-04  454            return;
> 18bf2805d9b30c kernel/sched/debug.c Ben Segall               2012-10-04  455
> ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  456    PN(se->exec_start);
> ff9b48c3598732 kernel/sched_debug.c Bharata B Rao            2008-11-10  457    PN(se->vruntime);
>
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
>


--
Thanks
Yafang

^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [peterz-queue:sched/core 13/19] kernel/sched/debug.c:453 print_cfs_group_stats() warn: variable dereferenced before check 'se' (see line 444)
  2021-09-13 11:04 ` Yafang Shao
@ 2021-09-13 12:02   ` Peter Zijlstra
  0 siblings, 0 replies; 3+ messages in thread
From: Peter Zijlstra @ 2021-09-13 12:02 UTC (permalink / raw)
  To: Yafang Shao; +Cc: Dan Carpenter, kbuild, kbuild test robot, kbuild-all, LKML

On Mon, Sep 13, 2021 at 07:04:14PM +0800, Yafang Shao wrote:
> Hi Peter,
> 
> Could you pls. help amend below change to the original commit ?

Yep, will do, thanks!

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-09-13 12:03 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-09-13  8:47 [peterz-queue:sched/core 13/19] kernel/sched/debug.c:453 print_cfs_group_stats() warn: variable dereferenced before check 'se' (see line 444) Dan Carpenter
2021-09-13 11:04 ` Yafang Shao
2021-09-13 12:02   ` Peter Zijlstra

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