elf: Fix LD_AUDIT for modules with invalid version (BZ#24122)

The error handling patch for invalid audit modules version access
invalid memory:

elf/rtld.c:

1454               unsigned int (*laversion) (unsigned int);
1455               unsigned int lav;
1456               if  (err_str == NULL
1457                    && (laversion = largs.result) != NULL
1458                    && (lav = laversion (LAV_CURRENT)) > 0
1459                    && lav <= LAV_CURRENT)
1460                 {
[...]
1526               else
1527                 {
1528                   /* We cannot use the DSO, it does not have the
1529                      appropriate interfaces or it expects something
1530                      more recent.  */
1531 #ifndef NDEBUG
1532                   Lmid_t ns = dlmargs.map->l_ns;
1533 #endif
1534                   _dl_close (dlmargs.map);
1535
1536                   /* Make sure the namespace has been cleared entirely.  */
1537                   assert (GL(dl_ns)[ns]._ns_loaded == NULL);
1538                   assert (GL(dl_ns)[ns]._ns_nloaded == 0);
1539
1540                   GL(dl_tls_max_dtv_idx) = tls_idx;
1541                   goto not_loaded;
1542                 }

1431           const char *err_str = NULL;
1432           bool malloced;
1433           (void) _dl_catch_error (&objname, &err_str, &malloced, dlmopen_doit,
1434                                   &dlmargs);
1435           if (__glibc_unlikely (err_str != NULL))
1436             {
1437             not_loaded:
1438               _dl_error_printf ("\
1439 ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
1440                                 name, err_str);
1441               if (malloced)
1442                 free ((char *) err_str);
1443             }

On failure the err_str will be NULL and _dl_debug_vdprintf does not handle
it properly:

elf/dl-misc.c:
200             case 's':
201               /* Get the string argument.  */
202               iov[niov].iov_base = va_arg (arg, char *);
203               iov[niov].iov_len = strlen (iov[niov].iov_base);
204               if (prec != -1)
205                 iov[niov].iov_len = MIN ((size_t) prec, iov[niov].iov_len);
206               ++niov;
207               break;

This patch fixes the issues and improves the error message.

Checked on x86_64-linux-gnu and i686-linux-gnu

	[BZ #24122]
	* elf/Makefile (tests): Add tst-audit13.
	(modules-names): Add tst-audit13mod1.
	(tst-audit13.out, LDFLAGS-tst-audit13mod1.so, tst-audit13-ENV): New
	rule.
	* elf/rtld.c (dl_main): Handle invalid audit module version.
	* elf/tst-audit13.c: New file.
	* elf/tst-audit13mod1.c: Likewise.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 93 insertions, 0 deletions

diff --git a/elf/tst-audit13mod1.c b/elf/tst-audit13mod1.c
new file mode 100644
index 0000000000..cf017e235c
--- /dev/null
+++ b/elf/tst-audit13mod1.c
@@ -0,0 +1,93 @@
+/* Check for invalid audit version (BZ#24122).
+   Copyright (C) 2019 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <link.h>
+#include <stdlib.h>
+
+unsigned int
+la_version (unsigned int version)
+{
+  /* The audit specification says that a version of 0 or a version
+     greater than any version supported by the dynamic loader shall
+     cause the module to be ignored.  */
+  return 0;
+}
+
+void
+la_activity (uintptr_t *cookie, unsigned int flag)
+{
+  exit (EXIT_FAILURE);
+}
+
+char *
+la_objsearch (const char *name, uintptr_t *cookie, unsigned int flag)
+{
+  exit (EXIT_FAILURE);
+}
+
+unsigned int
+la_objopen (struct link_map *map, Lmid_t lmid, uintptr_t * cookie)
+{
+  exit (EXIT_FAILURE);
+}
+
+void
+la_preinit (uintptr_t * cookie)
+{
+  exit (EXIT_FAILURE);
+}
+
+uintptr_t
+#if __ELF_NATIVE_CLASS == 32
+la_symbind32 (Elf32_Sym *sym, unsigned int ndx, uintptr_t *refcook,
+              uintptr_t *defcook, unsigned int *flags, const char *symname)
+#else
+la_symbind64 (Elf64_Sym *sym, unsigned int ndx, uintptr_t *refcook,
+              uintptr_t *defcook, unsigned int *flags, const char *symname)
+#endif
+{
+  exit (EXIT_FAILURE);
+}
+
+unsigned int
+la_objclose (uintptr_t * cookie)
+{
+  exit (EXIT_FAILURE);
+}
+
+#include <tst-audit.h>
+#if (!defined (pltenter) || !defined (pltexit) || !defined (La_regs) \
+     || !defined (La_retval) || !defined (int_retval))
+# error "architecture specific code needed in sysdeps/CPU/tst-audit.h"
+#endif
+
+ElfW(Addr)
+pltenter (ElfW(Sym) *sym, unsigned int ndx, uintptr_t *refcook,
+          uintptr_t *defcook, La_regs *regs, unsigned int *flags,
+          const char *symname, long int *framesizep)
+{
+  exit (EXIT_FAILURE);
+}
+
+unsigned int
+pltexit (ElfW(Sym) *sym, unsigned int ndx, uintptr_t *refcook,
+         uintptr_t *defcook, const La_regs *inregs, La_retval *outregs,
+         const char *symname)
+{
+  exit (EXIT_FAILURE);
+}