[Bug dynamic-link/18676] New: RTLD_NODELETE on an already open DSO does not prevent unloading

["siddhesh at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=18676

            Bug ID: 18676
           Summary: RTLD_NODELETE on an already open DSO does not prevent
                    unloading
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: dynamic-link
          Assignee: siddhesh at redhat dot com
          Reporter: siddhesh at redhat dot com
  Target Milestone: ---

Loading an already opened DSO with RTLD_NODELETE does not prevent the DSO from
being unloaded.  A simple program below demonstrates this:

cat > test.c
include <dlfcn.h>
#include <stdio.h>

int
do_test (void)
{
  void *h1 = dlopen ("$ORIGIN/tst-nodelete-opened-lib.so", RTLD_LAZY);
  if (h1 == NULL)
    {
      printf ("h1: failed to open DSO: %s\n", dlerror ());
      return 1;
    }

  void *h2 = dlopen ("$ORIGIN/tst-nodelete-opened-lib.so",
                     RTLD_LAZY | RTLD_NODELETE);
  if (h2 == NULL)
    {
      printf ("h2: failed to open DSO: %s\n", dlerror ());
      return 1;
    }

  int *foo = dlsym (h2, "foo_var");
  if (foo == NULL)
    {
      printf ("failed to load symbol foo_var: %s\n", dlerror ());
      return 1;
    }

  dlclose (h1);
  dlclose (h2);

  printf ("foo == %d\n", *foo);

  return 0;
}

#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"

cat > tst-nodelete-opened-lib.c
int foo_var = 42;

Expected result:

No segfault.

Actual Result:

Segfault.

Patch coming up.

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