commit 254d3d5aef2fd8430c469e1938209ac100ebf132

Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>

Date:   Mon Jan 24 10:46:16 2022 -0300

    elf: Fix initial-exec TLS access on audit modules (BZ #28096)

    For audit modules and dependencies with initial-exec TLS, we can not

    set the initial TLS image on default loader initialization because it

    would already be set by the audit setup.  However, subsequent thread

    creation would need to follow the default behaviour.

    This patch fixes it by setting l_auditing link_map field not only

    for the audit modules, but also for all its dependencies.  This is

    used on _dl_allocate_tls_init to avoid the static TLS initialization

    at load time.

    Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.

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

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

diff --git a/elf/Makefile b/elf/Makefile

index e4955c9f575f9015..3f5f72257a5fbea4 100644

--- a/elf/Makefile

+++ b/elf/Makefile

@@ -344,6 +344,7 @@ tests += \

   tst-audit19b \

   tst-audit2 \

   tst-audit20 \

+  tst-audit21 \

   tst-audit22 \

   tst-audit23 \

   tst-audit8 \

@@ -631,6 +632,8 @@ modules-names = \

   tst-auditmod19a \

   tst-auditmod19b \

   tst-auditmod20 \

+  tst-auditmod21a \

+  tst-auditmod21b \

   tst-auditmod22 \

   tst-auditmod23 \

   tst-big-note-lib \

@@ -2041,6 +2044,11 @@ $(objpfx)tst-audit20.out: $(objpfx)tst-auditmod20.so

 tst-audit20-ENV = LD_AUDIT=$(objpfx)tst-auditmod20.so

 $(objpfx)tst-auditmod20.so: $(libdl)

+$(objpfx)tst-audit21: $(shared-thread-library)

+$(objpfx)tst-audit21.out: $(objpfx)tst-auditmod21a.so

+$(objpfx)tst-auditmod21a.so: $(objpfx)tst-auditmod21b.so

+tst-audit21-ENV = LD_AUDIT=$(objpfx)tst-auditmod21a.so

+

 $(objpfx)tst-audit22.out: $(objpfx)tst-auditmod22.so

 tst-audit22-ARGS = -- $(host-test-program-cmd)

diff --git a/elf/dl-tls.c b/elf/dl-tls.c

index 7865fc390c3f3f0a..a918e9a6f585eb72 100644

--- a/elf/dl-tls.c

+++ b/elf/dl-tls.c

@@ -514,8 +514,12 @@ _dl_resize_dtv (dtv_t *dtv, size_t max_modid)

 }

+/* Allocate initial TLS.  RESULT should be a non-NULL pointer to storage

+   for the TLS space.  The DTV may be resized, and so this function may

+   call malloc to allocate that space.  The loader's GL(dl_load_tls_lock)

+   is taken when manipulating global TLS-related data in the loader.  */

 void *

-_dl_allocate_tls_init (void *result)

+_dl_allocate_tls_init (void *result, bool init_tls)

 {

   if (result == NULL)

     /* The memory allocation failed.  */

@@ -588,7 +592,14 @@ _dl_allocate_tls_init (void *result)

 	     some platforms use in static programs requires it.  */

 	  dtv[map->l_tls_modid].pointer.val = dest;

-	  /* Copy the initialization image and clear the BSS part.  */

+	  /* Copy the initialization image and clear the BSS part.  For

+	     audit modules or dependencies with initial-exec TLS, we can not

+	     set the initial TLS image on default loader initialization

+	     because it would already be set by the audit setup.  However,

+	     subsequent thread creation would need to follow the default

+	     behaviour.   */

+	  if (map->l_ns != LM_ID_BASE && !init_tls)

+	    continue;

 	  memset (__mempcpy (dest, map->l_tls_initimage,

 			     map->l_tls_initimage_size), '\0',

 		  map->l_tls_blocksize - map->l_tls_initimage_size);

@@ -615,7 +626,7 @@ _dl_allocate_tls (void *mem)

 {

   return _dl_allocate_tls_init (mem == NULL

 				? _dl_allocate_tls_storage ()

-				: allocate_dtv (mem));

+				: allocate_dtv (mem), true);

 }

 rtld_hidden_def (_dl_allocate_tls)

diff --git a/elf/rtld.c b/elf/rtld.c

index efcbeac6c24c4b7b..caa980dbda3d1a72 100644

--- a/elf/rtld.c

+++ b/elf/rtld.c

@@ -2421,7 +2421,7 @@ ERROR: '%s': cannot process note segment.\n", _dl_argv[0]);

      into the main thread's TLS area, which we allocated above.

      Note: thread-local variables must only be accessed after completing

      the next step.  */

-  _dl_allocate_tls_init (tcbp);

+  _dl_allocate_tls_init (tcbp, false);

   /* And finally install it for the main thread.  */

   if (! tls_init_tp_called)

diff --git a/elf/tst-audit21.c b/elf/tst-audit21.c

new file mode 100644

index 0000000000000000..3a47ab64d44421ee

--- /dev/null

+++ b/elf/tst-audit21.c

@@ -0,0 +1,42 @@

+/* Check LD_AUDIT with static TLS.

+   Copyright (C) 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 <ctype.h>

+#include <support/xthread.h>

+#include <support/check.h>

+

+static volatile __thread int out __attribute__ ((tls_model ("initial-exec")));

+

+static void *

+tf (void *arg)

+{

+  TEST_COMPARE (out, 0);

+  out = isspace (' ');

+  return NULL;

+}

+

+int main (int argc, char *argv[])

+{

+  TEST_COMPARE (out, 0);

+  out = isspace (' ');

+

+  pthread_t t = xpthread_create (NULL, tf, NULL);

+  xpthread_join (t);

+

+  return 0;

+}

diff --git a/elf/tst-auditmod21a.c b/elf/tst-auditmod21a.c

new file mode 100644

index 0000000000000000..f6d51b5c0531c49d

--- /dev/null

+++ b/elf/tst-auditmod21a.c

@@ -0,0 +1,80 @@

+/* Check LD_AUDIT with static TLS.

+   Copyright (C) 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 <ctype.h>

+#include <stdlib.h>

+#include <link.h>

+

+#define tls_ie __attribute__ ((tls_model ("initial-exec")))

+

+__thread int tls_var0 tls_ie;

+__thread int tls_var1 tls_ie = 0x10;

+

+/* Defined at tst-auditmod21b.so  */

+extern __thread int tls_var2;

+extern __thread int tls_var3;

+

+static volatile int out;

+

+static void

+call_libc (void)

+{

+  /* isspace accesses the initial-exec glibc TLS variables, which are

+     setup in glibc initialization.  */

+  out = isspace (' ');

+}

+

+unsigned int

+la_version (unsigned int v)

+{

+  tls_var0 = 0x1;

+  if (tls_var1 != 0x10)

+    abort ();

+  tls_var1 = 0x20;

+

+  tls_var2 = 0x2;

+  if (tls_var3 != 0x20)

+    abort ();

+  tls_var3 = 0x40;

+

+  call_libc ();

+

+  return LAV_CURRENT;

+}

+

+unsigned int

+la_objopen (struct link_map* map, Lmid_t lmid, uintptr_t* cookie)

+{

+  call_libc ();

+  *cookie = (uintptr_t) map;

+  return 0;

+}

+

+void

+la_activity (uintptr_t* cookie, unsigned int flag)

+{

+  if (tls_var0 != 0x1 || tls_var1 != 0x20)

+    abort ();

+  call_libc ();

+}

+

+void

+la_preinit (uintptr_t* cookie)

+{

+  call_libc ();

+}

diff --git a/elf/tst-auditmod21b.c b/elf/tst-auditmod21b.c

new file mode 100644

index 0000000000000000..6ba5335b7514c674

--- /dev/null

+++ b/elf/tst-auditmod21b.c

@@ -0,0 +1,22 @@

+/* Check LD_AUDIT with static TLS.

+   Copyright (C) 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/>.  */

+

+#define tls_ie __attribute__ ((tls_model ("initial-exec")))

+

+__thread int tls_var2 tls_ie;

+__thread int tls_var3 tls_ie = 0x20;

diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c

index 5fa45b19987717e1..58170d9da2bf0fa6 100644

--- a/nptl/allocatestack.c

+++ b/nptl/allocatestack.c

@@ -244,7 +244,7 @@ get_cached_stack (size_t *sizep, void **memp)

   memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));

   /* Re-initialize the TLS.  */

-  _dl_allocate_tls_init (TLS_TPADJ (result));

+  _dl_allocate_tls_init (TLS_TPADJ (result), true);

   return result;

 }

diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h

index 29b77b35175c1116..73f4863fd43922b9 100644

--- a/sysdeps/generic/ldsodefs.h

+++ b/sysdeps/generic/ldsodefs.h

@@ -1182,7 +1182,7 @@ extern void _dl_allocate_static_tls (struct link_map *map) attribute_hidden;

 /* These are internal entry points to the two halves of _dl_allocate_tls,

    only used within rtld.c itself at startup time.  */

 extern void *_dl_allocate_tls_storage (void) attribute_hidden;

-extern void *_dl_allocate_tls_init (void *);

+extern void *_dl_allocate_tls_init (void *, bool);

 rtld_hidden_proto (_dl_allocate_tls_init)

 /* Deallocate memory allocated with _dl_allocate_tls.  */