linux-kernel - Re: [PATCH v3] cpupower:Fix resource leaks in sysfs_get

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Date:   Tue, 18 Apr 2023 10:21:09 +0800
From:   Hao Zeng <zenghao@...inos.cn>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     trenn@...e.com, shuah@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] cpupower:Fix resource leaks in sysfs_get_enabled()

Dear Shuah:

Thank you again for your patience and guidance. This has benefited me a
lot. I will apply what I have learned this time to my work and kernel
contribution

Best regards
-- Hao

On Mon, 2023-04-17 at 15:09 -0600, Shuah Khan wrote:
> On 4/17/23 01:56, Hao Zeng wrote:
> > The sysfs_get_enabled() opened file processor not closed,
> > may cause a file handle leak.
> > Putting error handling and resource cleanup code together
> > makes the code easy to maintain and read.
> > Removed the unnecessary else if branch from the original
> > function, as it should return an error in cases other than '0'.
> > 
> > Signed-off-by: Hao Zeng <zenghao@...inos.cn>
> > Suggested-by: Shuah Khan <skhan@...uxfoundation.org>
> > ---
> >   tools/power/cpupower/lib/powercap.c | 22 ++++++++++++++--------
> >   1 file changed, 14 insertions(+), 8 deletions(-)
> > 
> > diff --git a/tools/power/cpupower/lib/powercap.c
> > b/tools/power/cpupower/lib/powercap.c
> > index 0ce29ee4c2e4..f0334a5f1acf 100644
> > --- a/tools/power/cpupower/lib/powercap.c
> > +++ b/tools/power/cpupower/lib/powercap.c
> > @@ -40,25 +40,31 @@ static int sysfs_get_enabled(char *path, int
> > *mode)
> >   {
> >         int fd;
> >         char yes_no;
> > +       int ret = 0;
> >   
> >         *mode = 0;
> >   
> >         fd = open(path, O_RDONLY);
> > -       if (fd == -1)
> > -               return -1;
> > +       if (fd == -1) {
> > +               ret = -1;
> > +               goto out;
> > +       }
> >   
> >         if (read(fd, &yes_no, 1) != 1) {
> > -               close(fd);
> > -               return -1;
> > +               ret = -1;
> > +               goto out_close;
> >         }
> >   
> >         if (yes_no == '1') {
> >                 *mode = 1;
> > -               return 0;
> 
> You can just add goto out_close here
> 
> > -       } else if (yes_no == '0') {
> > -               return 0;
> 
> Keep == '0' check and add goto out_close here
> > +       } else if (yes_no != '0') {
> 
> This can be just else with the above change.
> 
> > +               ret = -1;
> > +               goto out_close;
> >         }
> > -       return -1;
> > +out_close:
> > +       close(fd);
> > +out:
> > +       return ret;
> >   }
> >   
> >   int powercap_get_enabled(int *mode)
> 
> thanks,
> -- Shuah