Fix BZ 23400 -- stdlib/test-bz22786.c creates temporary files in glibc source tree

  Thanks for review!

On Mon, Jul 30, 2018 at 1:13 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:

> > +  strcpy (lnk, dir);
> > +  strcat (lnk, "/symlink");
>
> Maybe just 'char *lnk = xasprintf ("%s/symlink", dir);' instead?

Done.

> > +  if (symlink (".", lnk) != 0)
> >      {
> >        printf ("symlink (%s, %s): %m\n", dir, lnk);
> >        return EXIT_FAILURE;
>
> Use FAIL_EXIT1 or just TEST_VERIFY_EXIT.

Done.

> >    memset (p, 'a', path_len - (path - p) - 2);
> >    p[path_len - (path - p) - 1] = '\0';
>
> Shouldn't it 'p - path' instead? The subtraction is clearly issuing a
> overflow and I think it is not what the test meant here.

Good catch. Turns out that this was a buffer overflow in the original
test. Fixed.

Thanks,

2018-08-06  Paul Pluzhnikov  <ppluzhnikov@google.com>

        [BZ #23400]
        * stdlib/test-bz22786.c (do_test): Fix undefined behavior.
  

On 06/08/2018 12:12, Paul Pluzhnikov wrote:
> Thanks for review!
> 
> On Mon, Jul 30, 2018 at 1:13 PM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
> 
>>> +  strcpy (lnk, dir);
>>> +  strcat (lnk, "/symlink");
>> Maybe just 'char *lnk = xasprintf ("%s/symlink", dir);' instead?
> Done.
> 
>>> +  if (symlink (".", lnk) != 0)
>>>      {
>>>        printf ("symlink (%s, %s): %m\n", dir, lnk);
>>>        return EXIT_FAILURE;
>> Use FAIL_EXIT1 or just TEST_VERIFY_EXIT.
> Done.
> 
>>>    memset (p, 'a', path_len - (path - p) - 2);
>>>    p[path_len - (path - p) - 1] = '\0';
>> Shouldn't it 'p - path' instead? The subtraction is clearly issuing a
>> overflow and I think it is not what the test meant here.
> Good catch. Turns out that this was a buffer overflow in the original
> test. Fixed.
> 
> Thanks,
> 
> 2018-08-06  Paul Pluzhnikov  <ppluzhnikov@google.com>
> 
>         [BZ #23400]
>         * stdlib/test-bz22786.c (do_test): Fix undefined behavior.

Add that it fix the temporary file creation in glibc source tree as
well. LGTM, thanks.

> 
> -- Paul Pluzhnikov
> 
> 
> glibc-bz23400-20180805.txt
> 
> 
> diff --git a/stdlib/test-bz22786.c b/stdlib/test-bz22786.c
> index e7837f98c1..879d61dafa 100644
> --- a/stdlib/test-bz22786.c
> +++ b/stdlib/test-bz22786.c
> @@ -26,28 +26,20 @@
>  #include <unistd.h>
>  #include <sys/stat.h>
>  #include <sys/types.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/temp_file.h>
>  #include <support/test-driver.h>
>  #include <libc-diag.h>
>  
>  static int
>  do_test (void)
>  {
> -  const char dir[] = "bz22786";
> -  const char lnk[] = "bz22786/symlink";
> +  const char *dir = support_create_temp_directory ("bz22786.");
> +  const char *lnk = xasprintf ("%s/symlink", dir);
> +  const size_t path_len = (size_t) INT_MAX + strlen (lnk) + 1;
>  
> -  rmdir (dir);
> -  if (mkdir (dir, 0755) != 0 && errno != EEXIST)
> -    {
> -      printf ("mkdir %s: %m\n", dir);
> -      return EXIT_FAILURE;
> -    }
> -  if (symlink (".", lnk) != 0 && errno != EEXIST)
> -    {
> -      printf ("symlink (%s, %s): %m\n", dir, lnk);
> -      return EXIT_FAILURE;
> -    }
> -
> -  const size_t path_len = (size_t) INT_MAX + 1;
> +  TEST_VERIFY_EXIT (symlink (".", lnk) == 0);
>  
>    DIAG_PUSH_NEEDS_COMMENT;
>  #if __GNUC_PREREQ (7, 0)
> @@ -55,20 +47,14 @@ do_test (void)
>       allocation to succeed for the test to work.  */
>    DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
>  #endif
> -  char *path = malloc (path_len);
> +  char *path = xmalloc (path_len);
>    DIAG_POP_NEEDS_COMMENT;
>  
> -  if (path == NULL)
> -    {
> -      printf ("malloc (%zu): %m\n", path_len);
> -      return EXIT_UNSUPPORTED;
> -    }
> -
> -  /* Construct very long path = "bz22786/symlink/aaaa....."  */
> -  char *p = mempcpy (path, lnk, sizeof (lnk) - 1);
> +  /* Construct very long path = "/tmp/bz22786.XXXX/symlink/aaaa....."  */
> +  char *p = mempcpy (path, lnk, strlen (lnk));
>    *(p++) = '/';
> -  memset (p, 'a', path_len - (path - p) - 2);
> -  p[path_len - (path - p) - 1] = '\0';
> +  memset (p, 'a', path_len - (p - path) - 2);
> +  p[path_len - (p - path) - 1] = '\0';
>  
>    /* This call crashes before the fix for bz22786 on 32-bit platforms.  */
>    p = realpath (path, NULL);
> @@ -81,7 +67,6 @@ do_test (void)
>  
>    /* Cleanup.  */
>    unlink (lnk);
> -  rmdir (dir);
>  
>    return 0;
>  }
>