dlsym: Make RTLD_NEXT prefer default version definition [BZ #14932]

When the first object providing foo defines both foo@v1 and foo@@v2,
dlsym(RTLD_NEXT, "foo") returns foo@v1 while dlsym(RTLD_DEFAULT, "foo")
returns foo@@v2.  The issue is that RTLD_DEFAULT uses the
DL_LOOKUP_RETURN_NEWEST flag while RTLD_NEXT doesn't.  Fix the RTLD_NEXT
branch to use DL_LOOKUP_RETURN_NEWEST.

Note: the new behavior matches FreeBSD rtld.  Future sanitizers will not
need to add versioned interceptors like https://reviews.llvm.org/D96348

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/elf/tst-next-ver.c b/elf/tst-next-ver.c
new file mode 100644
index 0000000000..7241f9038b
--- /dev/null
+++ b/elf/tst-next-ver.c
@@ -0,0 +1,46 @@
+/* Test RTLD_DEFAULT/RTLD_NEXT when the definition has multiple versions.
+   Copyright (C) 2018-2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <stdio.h>
+
+#include "testobj.h"
+
+static int
+do_test (void)
+{
+  /* Resolve to foo@@v3 in nextmod3.so, instead of
+     foo@v1 or foo@v2.  */
+  int (*fp) (int) = dlsym (RTLD_DEFAULT, "foo");
+  int res = fp (0);
+  printf ("preload (0) = %d, %s\n", res, res == 3 ? "ok" : "wrong");
+  if (res != 3)
+    return 1;
+
+  /* Resolve to foo@@v3 in nextmod3.so, instead of
+     foo@v1 or foo@v2.  */
+  fp = dlsym (RTLD_NEXT, "foo");
+  res = fp (0);
+  printf ("preload (0) = %d, %s\n", res, res == 3 ? "ok" : "wrong");
+  if (res != 3)
+    return 1;
+
+  return 0;
+}
+
+#include <support/test-driver.c>