Re: [patch] Fix BZ 23400 -- stdlib/test-bz22786.c creates temporary files in glibc source tree

[Stefan Liebler <stli at linux dot ibm dot com>]

Hi Paul,

If I run the test on s390 (31bit), the test fails with:
malloc: unable to allocate 2147483675 bytes: Cannot allocate memory
warning: could not remove temporary file: /tmp/bz22786.iaoLYS: Directory 
not empty

This test tries to allocate a little bit too much bytes for 31bit. Thus 
the former implementation returned EXIT_UNSUPPORTED. Now the test is 
failing due to xmalloc.

As the symlink was created within the temporary directory 
/tmp/bz22786.XXXXXX, but was not unlinked by the test, 
support_delete_temp_files() fails to remove it.

Can we just return EXIT_UNSUPPORTED on 31bit as done with the attached 
patch?

Bye
Stefan

On 08/06/2018 05:12 PM, 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.

commit 5ada1975be8f1b30b8f33d1d25cb5575690066e1
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Wed Aug 29 15:20:51 2018 +0200

    Test stdlib/test-bz22786 exits now with unsupported if malloc fails.
    
    The test tries to allocate more than 2^31 bytes which will always fail on s390
    as it has maximum 31bit of memory.
    Before commit 6c3a8a9d868a8deddf0d6dcc785b6d120de90523, this test returned
    unsupported if malloc fails.  This patch re enables this behaviour.
    
    Furthermore support_delete_temp_files() failed to remove the temp directory
    in this case as it is not empty due to the created symlink.
    Thus the creation of the symlink is moved behind malloc.
    
    ChangeLog
    
            * stdlib/test-bz22786.c (do_test): Return EXIT_UNSUPPORTED
            if malloc fails.

diff --git a/stdlib/test-bz22786.c b/stdlib/test-bz22786.c
index d1aa69106c..44ec631a96 100644
--- a/stdlib/test-bz22786.c
+++ b/stdlib/test-bz22786.c
@@ -39,16 +39,21 @@ do_test (void)
   const char *lnk = xasprintf ("%s/symlink", dir);
   const size_t path_len = (size_t) INT_MAX + strlen (lnk) + 1;
 
-  TEST_VERIFY_EXIT (symlink (".", lnk) == 0);
-
   DIAG_PUSH_NEEDS_COMMENT;
 #if __GNUC_PREREQ (7, 0)
   /* GCC 7 warns about too-large allocations; here we need such
      allocation to succeed for the test to work.  */
   DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
 #endif
-  char *path = xmalloc (path_len);
+  char *path = malloc (path_len);
   DIAG_POP_NEEDS_COMMENT;
+  if (path == NULL)
+    {
+      printf ("malloc (%zu): %m\n", path_len);
+      return EXIT_UNSUPPORTED;
+    }
+
+  TEST_VERIFY_EXIT (symlink (".", lnk) == 0);
 
   /* Construct very long path = "/tmp/bz22786.XXXX/symlink/aaaa....."  */
   char *p = mempcpy (path, lnk, strlen (lnk));