elf: Always set l in _dl_init_paths (bug 23462)

After d1d5471579eb0426671bf94f2d71e61dfb204c30 ("Remove dead
DL_DST_REQ_STATIC code.") we always setup the link map l to make the
static and shared cases the same.  The bug is that in elf/dl-load.c
(_dl_init_paths) we conditionally set l only in the #ifdef SHARED
case, but unconditionally use it later.  The simple solution is to
remove the #ifdef SHARED conditional, because it's no longer needed,
and unconditionally setup l for both the static and shared cases. A
regression test is added to run a static binary with
LD_LIBRARY_PATH='$ORIGIN' which crashes before the fix and runs after
the fix.

Co-Authored-By: Florian Weimer <fweimer@redhat.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/elf/tst-dst-static.c b/elf/tst-dst-static.c
new file mode 100644
index 0000000..56eb371
--- /dev/null
+++ b/elf/tst-dst-static.c
@@ -0,0 +1,32 @@
+/* Test DST expansion for static binaries doesn't carsh.  Bug 23462.
+   Copyright (C) 2021 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/>.  */
+
+/* The purpose of this test is to exercise the code in elf/dl-loac.c
+   (_dl_init_paths) or thereabout and ensure that static binaries
+   don't crash when expanding DSTs.
+
+   If the dynamic loader code linked into the static binary cannot
+   handle expanding the DSTs e.g. null-deref on an incomplete link
+   map, then it will crash before reaching main, so the test harness
+   is unnecessary.  */
+
+int
+main (void)
+{
+  return 0;
+}