[CRIU] [PATCH 5/8] cgroup: don't use fread in read_cgroup_prop()

[Tycho Andersen]

On Fri, Oct 31, 2014 at 07:22:36PM +0300, Andrey Vagin wrote:
> I think this version of code is a bit more readable.
> It doesn't do memcpy and doesn't allocate FILE.
> Everyone knows arguments for read(), but only a few of
> us know arguments for fread().
> 
> CID 73345 (#1 of 1): String not null terminated (STRING_NULL)
> 2. string_null_argument: Function fread does not terminate string *buf. [Note: The source code implementation of the function has been overridden by a builtin model.]
> 
> Cc: Tycho Andersen <tycho.andersen at canonical.com>

Acked-by: Tycho Andersen <tycho.andersen at canonical.com>

> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  cgroup.c | 27 +++++++++++----------------
>  1 file changed, 11 insertions(+), 16 deletions(-)
> 
> diff --git a/cgroup.c b/cgroup.c
> index fb5c8ac..f5da3ed 100644
> --- a/cgroup.c
> +++ b/cgroup.c
> @@ -305,31 +305,26 @@ static inline char *strip(char *str)
>  static int read_cgroup_prop(struct cgroup_prop *property, const char *fullpath)
>  {
>  	char buf[1024];
> -	FILE *f;
> -	char *endptr;
> +	int fd, ret;
>  
> -	f = fopen(fullpath, "r");
> -	if (!f) {
> +	fd = open(fullpath, O_RDONLY);
> +	if (fd == -1) {
>  		property->value = NULL;
>  		pr_perror("Failed opening %s", fullpath);
>  		return -1;
>  	}
>  
> -	memset(buf, 0, sizeof(buf));
> -	if (fread(buf, sizeof(buf), 1, f) != 1) {
> -		if (!feof(f)) {
> -			pr_err("Failed scanning %s\n", fullpath);
> -			fclose(f);
> -			return -1;
> -		}
> -	}
> -
> -	if (fclose(f) != 0) {
> -		pr_err("Failed closing %s\n", fullpath);
> +	ret = read(fd, buf, sizeof(buf) - 1);
> +	if (ret == -1) {
> +		pr_err("Failed scanning %s\n", fullpath);
> +		close(fd);
>  		return -1;
>  	}
> +	close(fd);
> +
> +	buf[ret] = 0;
>  
> -	if (strtoll(buf, &endptr, 10) == LLONG_MAX)
> +	if (strtoll(buf, NULL, 10) == LLONG_MAX)
>  		strcpy(buf, "-1");
>  
>  	property->value = xstrdup(strip(buf));
> -- 
> 1.9.3
>