linux-kernel - Re: [PATCH] selftests: cgroup: Fix unsigned comparison with less than zero

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Message-ID: <Y2mqNtqpmRnEBxcC@P9FQF9L96D>
Date:   Mon, 7 Nov 2022 17:00:38 -0800
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     tj@...nel.org, lizefan.x@...edance.com, hannes@...xchg.org,
        shuah@...nel.org, yosryahmed@...gle.com, shakeelb@...gle.com,
        rientjes@...gle.com, akpm@...ux-foundation.org,
        cgroups@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: cgroup: Fix unsigned comparison with less
 than zero

On Sat, Nov 05, 2022 at 07:06:11PM +0800, YueHaibing wrote:
> 'size' is unsigned, it never less than zero.
> 
> Fixes: 6c26df84e1f2 ("selftests: cgroup: return -errno from cg_read()/cg_write() on failure")
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  tools/testing/selftests/cgroup/cgroup_util.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/cgroup/cgroup_util.c b/tools/testing/selftests/cgroup/cgroup_util.c
> index 4c52cc6f2f9c..e8bbbdb77e0d 100644
> --- a/tools/testing/selftests/cgroup/cgroup_util.c
> +++ b/tools/testing/selftests/cgroup/cgroup_util.c
> @@ -555,6 +555,7 @@ int proc_mount_contains(const char *option)
>  ssize_t proc_read_text(int pid, bool thread, const char *item, char *buf, size_t size)
>  {
>  	char path[PATH_MAX];
> +	ssize_t ret;
>  
>  	if (!pid)
>  		snprintf(path, sizeof(path), "/proc/%s/%s",
> @@ -562,8 +563,8 @@ ssize_t proc_read_text(int pid, bool thread, const char *item, char *buf, size_t
>  	else
>  		snprintf(path, sizeof(path), "/proc/%d/%s", pid, item);
>  
> -	size = read_text(path, buf, size);
> -	return size < 0 ? -1 : size;
> +	ret = read_text(path, buf, size);
> +	return ret < 0 ? -1 : ret;
>  }

Indeed, good catch!

Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>

Thanks!