[PATCH] lib: fwts_cpu.c: fix time-of-use race on stat/open (LP: #1209225)

[Keng-Yu Lin]

On Wed, Aug 7, 2013 at 8:42 PM, Colin King <colin.king at canonical.com> wrote:
> From: Colin Ian King <colin.king at canonical.com>
>
> Coverity Scan reports that the stat/open may give a small window
> of opportunity for a stat/open race condition. So just forget the
> stat as open will do.
>
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> ---
>  src/lib/src/fwts_cpu.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/src/lib/src/fwts_cpu.c b/src/lib/src/fwts_cpu.c
> index 44711fd..fc52fa5 100644
> --- a/src/lib/src/fwts_cpu.c
> +++ b/src/lib/src/fwts_cpu.c
> @@ -51,30 +51,23 @@ static pid_t *fwts_cpu_pids;
>   */
>  int fwts_cpu_readmsr(const int cpu, const uint32_t reg, uint64_t *val)
>  {
> -       struct stat statbuf;
>         char buffer[PATH_MAX];
> -       uint64_t value;
> +       uint64_t value = 0;
>         int fd;
>         int ret;
>
> -       value = 0;
> -
>         snprintf(buffer, sizeof(buffer), "/dev/cpu/%d/msr", cpu);
> -
> -       if (stat(buffer, &statbuf)) {
> +       if ((fd = open(buffer, O_RDONLY)) < 0) {
>                 /* Hrm, msr not there, so force modprobe msr and see what happens */
>                 pid_t pid;
>                 if ((fd = fwts_pipe_open("modprobe msr", &pid)) < 0)
>                         return FWTS_ERROR;
>                 fwts_pipe_close(fd, pid);
>
> -               if (stat(buffer, &statbuf))
> +               if ((fd = open(buffer, O_RDONLY)) < 0)
>                         return FWTS_ERROR; /* Really failed */
>         }
>
> -       if ((fd = open(buffer, O_RDONLY)) < 0)
> -                return FWTS_ERROR;
> -
>         ret = pread(fd, &value, 8, reg);
>         close(fd);
>
> --
> 1.8.3.2
>

Acked-by: Keng-Yu Lin <kengyu at canonical.com>