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>

4 files changed, 153 insertions, 7 deletions

diff --git a/elf/Makefile b/elf/Makefile
index 9cf5cd8dfd..c24d765730 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -187,7 +187,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-nodelete2 tst-audit11 tst-audit12 tst-dlsym-error tst-noload \
 	 tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose \
 	 tst-debug1 tst-main1 tst-absolute-sym tst-absolute-zero tst-big-note \
-	 tst-unwind-ctor tst-unwind-main
+	 tst-unwind-ctor tst-unwind-main tst-audit13
 #	 reldep9
 tests-internal += loadtest unload unload2 circleload1 \
 	 neededtest neededtest2 neededtest3 neededtest4 \
@@ -275,7 +275,8 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-latepthreadmod $(tst-tls-many-dynamic-modules) \
 		tst-nodelete-dlclose-dso tst-nodelete-dlclose-plugin \
 		tst-main1mod tst-libc_dlvsym-dso tst-absolute-sym-lib \
-		tst-absolute-zero-lib tst-big-note-lib tst-unwind-ctor-lib
+		tst-absolute-zero-lib tst-big-note-lib tst-unwind-ctor-lib \
+		tst-audit13mod1
 # Most modules build with _ISOMAC defined, but those filtered out
 # depend on internal headers.
 modules-names-tests = $(filter-out ifuncmod% tst-libc_dlvsym-dso tst-tlsmod%,\
@@ -1382,6 +1383,10 @@ tst-audit12-ENV = LD_AUDIT=$(objpfx)tst-auditmod12.so
 $(objpfx)tst-audit12mod1.so: $(objpfx)tst-audit12mod2.so
 LDFLAGS-tst-audit12mod2.so = -Wl,--version-script=tst-audit12mod2.map
 
+$(objpfx)tst-audit13.out: $(objpfx)tst-audit13mod1.so
+LDFLAGS-tst-audit13mod1.so = -Wl,-z,lazy
+tst-audit13-ENV = LD_AUDIT=$(objpfx)tst-audit13mod1.so
+
 # Override -z defs, so that we can reference an undefined symbol.
 # Force lazy binding for the same reason.
 LDFLAGS-tst-latepthreadmod.so = \
diff --git a/elf/rtld.c b/elf/rtld.c
index 5d97f41b7b..9e0f752482 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1453,10 +1453,12 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
 
 	      unsigned int (*laversion) (unsigned int);
 	      unsigned int lav;
-	      if  (err_str == NULL
-		   && (laversion = largs.result) != NULL
-		   && (lav = laversion (LAV_CURRENT)) > 0
-		   && lav <= LAV_CURRENT)
+	      if (err_str != NULL)
+		goto not_loaded;
+
+	      if ((laversion = largs.result) != NULL
+		  && (lav = laversion (LAV_CURRENT)) > 0
+		  && lav <= LAV_CURRENT)
 		{
 		  /* Allocate structure for the callback function pointers.
 		     This call can never fail.  */
@@ -1538,7 +1540,25 @@ ERROR: ld.so: object '%s' cannot be loaded as audit interface: %s; ignored.\n",
 		  assert (GL(dl_ns)[ns]._ns_nloaded == 0);
 
 		  GL(dl_tls_max_dtv_idx) = tls_idx;
-		  goto not_loaded;
+		  if (GLRO(dl_debug_mask) & DL_DEBUG_FILES)
+		    {
+		      _dl_debug_printf ("\
+\nfile=%s cannot be loaded as audit interface; ignored.\n", name);
+		      if (laversion == NULL)
+			_dl_debug_printf (
+"  la_version function not found.\n");
+		      else
+			{
+			  if (lav == 0)
+			    _dl_debug_printf (
+"  auditor requested to be ignored (returned version of 0).\n");
+			  else
+			    _dl_debug_printf (
+"  auditor disabled since expected version %d is greater than "
+"supported version %d.\n",
+					      lav, LAV_CURRENT);
+			}
+		    }
 		}
 	    }
 	}
diff --git a/elf/tst-audit13.c b/elf/tst-audit13.c
new file mode 100644
index 0000000000..6f587baf58
--- /dev/null
+++ b/elf/tst-audit13.c
@@ -0,0 +1,28 @@
+/* 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 <stdio.h>
+
+static int
+do_test (void)
+{
+  puts ("plt call");
+  return 0;
+}
+
+#include <support/test-driver.c>
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);
+}