elf: Add elf/tst-dlopenfail-2 [BZ #25396]

Without CET, a jump into a newly loaded object through an overwritten
link map often does not crash, it just executes some random code.
CET detects this in some cases because the function pointer does not
point to the start of a function in the replacement shared object,
so there is no ENDBR instruction.

The new test uses a small shared object and the existing dangling
link map to trigger the bug.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/elf/tst-dlopenfailmod3.c b/elf/tst-dlopenfailmod3.c
new file mode 100644
index 0000000000..636e971264
--- /dev/null
+++ b/elf/tst-dlopenfailmod3.c
@@ -0,0 +1,17 @@
+/* Empty module for the tst-dlopenfail-2 test.
+   Copyright (C) 2020 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/>.  */