Re: [patch] Fix fileio.exp failuew when run as root user.

[Yao Qi <yao@codesourcery.com>]

On 11/20/2010 12:34 AM, Phil Muldoon wrote:
> 
> This patch has been carried in the Fedora RPM since 6.8. We are
> submitting it for inclusion upstream.
> 
> gdb.base/fileio.exp|c fail when this test is executed as a root.  This
> test fixes that.

I don't have Fedora system on hand, but I can reproduce this problem on
Ubuntu with 'sudo make check RUNTESTFLAGS="fileio.exp"', and get
following two fails.

FAIL: gdb.base/fileio.exp: Open for write but no write permission
returns EACCES
FAIL: gdb.base/fileio.exp: Unlinking a file in a directory w/o write
access returns EACCES

If they are what you want to fix in this patch, here is one cent,

>  int
>  main ()
>  {
> +  /* ROOTSUBDIR is already prepared by fileio.exp.  We use it for easy cleanup
> +     (by fileio.exp) if we are run by multiple users in the same directory.  */
> +
> +  if (chdir (ROOTSUBDIR) != 0)
> +    {
> +      printf ("chdir " ROOTSUBDIR ": %s\n", strerror (errno));
> +      exit (1);
> +    }
> +
> +  /* These tests
> +       Open for write but no write permission returns EACCES
> +       Unlinking a file in a directory w/o write access returns EACCES
> +     fail if we are being run as root - drop the privileges here.  */
> +
> +  if (geteuid () == 0)
> +    {
> +      uid_t uid = 99;
> +
> +      if (chown (".", uid, uid) != 0)
> +	{
> +	  printf ("chown %d.%d " ROOTSUBDIR ": %s\n", (int) uid, (int) uid,
> +		  strerror (errno));
> +	  exit (1);
> +	}
> +      if (setuid (uid) || geteuid () == 0)
> +	{
> +	  printf ("setuid %d: %s\n", (int) uid, strerror (errno));
> +	  exit (1);
> +	}
> +    }
> +

We can extract these code into a separate function, and replace
"exit(1)" by "return 1".

/* Try to drop root privileges of this process.  Return 0 if it is done
successfully, otherwise return non-zero.  */
int try_drop_root_privilege()
{
....
}

int
main ()
{
  if (try_drop_root_privilege())
    {
       exit (1);
    }
...
...
}

-- 
Yao (齐尧)