kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   36c254515dc6592c44db77b84908358979dd6b50
commit: 35f96de04127d332a5c5e8a155d31f452f88c76d bpf: Introduce BPF token object
date:   9 months ago
config: alpha-randconfig-r054-20241012 (https://download.01.org/0day-ci/archive/20241013/202410131412.5csjqw8L-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 13.3.0

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/202410131412.5csjqw8L-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

vim +50 kernel/bpf/token.c

    44	
    45	void bpf_token_put(struct bpf_token *token)
    46	{
    47		if (!token)
    48			return;
    49	
  > 50		if (!atomic64_dec_and_test(&token->refcnt))
    51			return;
    52	
    53		INIT_WORK(&token->work, bpf_token_put_deferred);
  > 54		schedule_work(&token->work);
    55	}
    56	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

[Andrii Nakryiko]

On Sat, Oct 12, 2024 at 11:58 PM kernel test robot <lkp@intel.com> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   36c254515dc6592c44db77b84908358979dd6b50
> commit: 35f96de04127d332a5c5e8a155d31f452f88c76d bpf: Introduce BPF token object
> date:   9 months ago
> config: alpha-randconfig-r054-20241012 (https://download.01.org/0day-ci/archive/20241013/202410131412.5csjqw8L-lkp@intel.com/config)
> compiler: alpha-linux-gcc (GCC) 13.3.0
>
> 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/202410131412.5csjqw8L-lkp@intel.com/
>
> cocci warnings: (new ones prefixed by >>)
> >> kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

Can someone please explain what this means and why the code below is
broken, according to coccinelle?

>
> vim +50 kernel/bpf/token.c
>
>     44
>     45  void bpf_token_put(struct bpf_token *token)
>     46  {
>     47          if (!token)
>     48                  return;
>     49
>   > 50          if (!atomic64_dec_and_test(&token->refcnt))
>     51                  return;
>     52
>     53          INIT_WORK(&token->work, bpf_token_put_deferred);
>   > 54          schedule_work(&token->work);

this is not "object free", but even if it was, I still don't see the
problem, tbh...

>     55  }
>     56
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   0fc810ae3ae110f9e2fcccce80fc8c8d62f97907
commit: 35f96de04127d332a5c5e8a155d31f452f88c76d bpf: Introduce BPF token object
date:   9 months ago
config: i386-randconfig-051-20241031 (https://download.01.org/0day-ci/archive/20241031/202410311704.yIRxjp0C-lkp@intel.com/config)
compiler: clang version 19.1.2 (https://github.com/llvm/llvm-project 7ba7d8e2f7b6445b60679da826210cdde29eaf8b)

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/202410311704.yIRxjp0C-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

vim +50 kernel/bpf/token.c

    44	
    45	void bpf_token_put(struct bpf_token *token)
    46	{
    47		if (!token)
    48			return;
    49	
  > 50		if (!atomic64_dec_and_test(&token->refcnt))
    51			return;
    52	
    53		INIT_WORK(&token->work, bpf_token_put_deferred);
  > 54		schedule_work(&token->work);
    55	}
    56	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   c061cf420ded391e32f99cd483e1e0107f213b12
commit: 35f96de04127d332a5c5e8a155d31f452f88c76d bpf: Introduce BPF token object
date:   11 months ago
config: hexagon-randconfig-r051-20241218 (https://download.01.org/0day-ci/archive/20241219/202412190521.9R1HKuug-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 2dc22615fd46ab2566d0f26d5ba234ab12dc4bf8)

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/202412190521.9R1HKuug-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> kernel/bpf/token.c:50:6-27: WARNING: atomic_dec_and_test variation before object free at line 54.

vim +50 kernel/bpf/token.c

    44	
    45	void bpf_token_put(struct bpf_token *token)
    46	{
    47		if (!token)
    48			return;
    49	
  > 50		if (!atomic64_dec_and_test(&token->refcnt))
    51			return;
    52	
    53		INIT_WORK(&token->work, bpf_token_put_deferred);
  > 54		schedule_work(&token->work);
    55	}
    56	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki