[v5,2/4] elf: Do not change stack permission on dlopen/dlmopen

diff --git a/NEWS b/NEWS
index dae2332eab..8cb5597631 100644
--- a/NEWS
+++ b/NEWS
@@ -49,6 +49,12 @@  Deprecated and removed features, and other changes affecting compatibility:
 
 * The nios2*-*-linux-gnu configurations are no longer supported.
 
+* dlopen and dlmopen no longer make the stack executable if a shared
+  library requires it, either implicitly because of a missing GNU_STACK ELF
+  header (and default ABI permission having the executable bit set) or
+  explicitly because of the executable bit in GNU_STACK, and the stack is
+  not already executable.
+
 Changes to build and runtime requirements:
 
 * On recent Linux kernels with vDSO getrandom support, getrandom does not
diff --git a/elf/dl-load.c b/elf/dl-load.c
index e986d7faab..f525eec662 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1282,12 +1282,13 @@  _dl_map_object_from_fd (const char *name, const char *origname, int fd,
   if (__glibc_unlikely ((stack_flags &~ GL(dl_stack_flags)) & PF_X))
     {
       /* The stack is presently not executable, but this module
-	 requires that it be executable.  */
-#if PTHREAD_IN_LIBC
-      errval = _dl_make_stacks_executable (stack_endp);
-#else
-      errval = (*GL(dl_make_stack_executable_hook)) (stack_endp);
-#endif
+	 requires that it be executable.  Only tries to change the
+	 stack protection during process startup.  */
+      if ((mode & __RTLD_DLOPEN) == 0)
+	errval = _dl_make_stack_executable (stack_endp);
+      else
+	errval = EINVAL;
+
       if (errval)
 	{
 	  errstring = N_("\
diff --git a/elf/dl-support.c b/elf/dl-support.c
index ee590edf93..fe1f8c8f6a 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -178,10 +178,6 @@  size_t _dl_stack_cache_actsize;
 uintptr_t _dl_in_flight_stack;
 int _dl_stack_cache_lock;
 #else
-/* If loading a shared object requires that we make the stack executable
-   when it was not, we do it by calling this function.
-   It returns an errno code or zero on success.  */
-int (*_dl_make_stack_executable_hook) (void **) = _dl_make_stack_executable;
 void (*_dl_init_static_tls) (struct link_map *) = &_dl_nothread_init_static_tls;
 #endif
 struct dl_scope_free_list *_dl_scope_free_list;
diff --git a/elf/rtld.c b/elf/rtld.c
index b8cc3f605f..3b232f8525 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -1335,12 +1335,6 @@  dl_main (const ElfW(Phdr) *phdr,
 
   __tls_pre_init_tp ();
 
-#if !PTHREAD_IN_LIBC
-  /* The explicit initialization here is cheaper than processing the reloc
-     in the _rtld_local definition's initializer.  */
-  GL(dl_make_stack_executable_hook) = &_dl_make_stack_executable;
-#endif
-
   /* Process the environment variable which control the behaviour.  */
   skip_env = process_envvars (&state);
 
diff --git a/elf/tst-execstack.c b/elf/tst-execstack.c
index 560b353918..cd758c089e 100644
--- a/elf/tst-execstack.c
+++ b/elf/tst-execstack.c
@@ -9,6 +9,11 @@ 
 #include <error.h>
 #include <stackinfo.h>
 
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/xthread.h>
+#include <support/xdlfcn.h>
+
 static void
 print_maps (void)
 {
@@ -20,11 +25,21 @@  print_maps (void)
 #endif
 }
 
-static void deeper (void (*f) (void));
+#ifndef DEFAULT_RWX_STACK
+# define DEFAULT_RWX_STACK 0
+#else
+static void
+deeper (void (*f) (void))
+{
+  char stack[1100 * 1024];
+  explicit_bzero (stack, sizeof stack);
+  (*f) ();
+  memfrob (stack, sizeof stack);
+}
+#endif
 
 #if USE_PTHREADS
-# include <pthread.h>
-
+# if DEFAULT_RWX_STACK
 static void *
 tryme_thread (void *f)
 {
@@ -32,16 +47,21 @@  tryme_thread (void *f)
 
   return 0;
 }
+# endif
 
 static pthread_barrier_t startup_barrier, go_barrier;
 static void *
 waiter_thread (void *arg)
 {
-  void **f = arg;
-  pthread_barrier_wait (&startup_barrier);
-  pthread_barrier_wait (&go_barrier);
+  xpthread_barrier_wait (&startup_barrier);
+  xpthread_barrier_wait (&go_barrier);
 
+# if DEFAULT_RWX_STACK
+  void **f = arg;
   (*((void (*) (void)) *f)) ();
+# else
+  abort ();
+# endif
 
   return 0;
 }
@@ -83,52 +103,36 @@  do_test (void)
 
   printf ("executable stacks %sallowed\n", allow_execstack ? "" : "not ");
 
+#if USE_PTHREADS || DEFAULT_RWX_STACK
   static void *f;		/* Address of this is used in other threads. */
+#endif
 
 #if USE_PTHREADS
   /* Create some threads while stacks are nonexecutable.  */
   #define N 5
-  pthread_t thr[N];
 
-  pthread_barrier_init (&startup_barrier, NULL, N + 1);
-  pthread_barrier_init (&go_barrier, NULL, N + 1);
+  xpthread_barrier_init (&startup_barrier, NULL, N + 1);
+  xpthread_barrier_init (&go_barrier, NULL, N + 1);
 
   for (int i = 0; i < N; ++i)
-    {
-      int rc = pthread_create (&thr[i], NULL, &waiter_thread, &f);
-      if (rc)
-	error (1, rc, "pthread_create");
-    }
+    xpthread_create (NULL, &waiter_thread, &f);
 
   /* Make sure they are all there using their stacks.  */
-  pthread_barrier_wait (&startup_barrier);
+  xpthread_barrier_wait (&startup_barrier);
   puts ("threads waiting");
 #endif
 
   print_maps ();
 
-#if USE_PTHREADS
+#if USE_PTHREADS && DEFAULT_RWX_STACK
   void *old_stack_addr, *new_stack_addr;
   size_t stack_size;
   pthread_t me = pthread_self ();
   pthread_attr_t attr;
-  int ret = 0;
-
-  ret = pthread_getattr_np (me, &attr);
-  if (ret)
-    {
-      printf ("before execstack: pthread_getattr_np returned error: %s\n",
-	      strerror (ret));
-      return 1;
-    }
 
-  ret = pthread_attr_getstack (&attr, &old_stack_addr, &stack_size);
-  if (ret)
-    {
-      printf ("before execstack: pthread_attr_getstack returned error: %s\n",
-	      strerror (ret));
-      return 1;
-    }
+  TEST_VERIFY_EXIT (pthread_getattr_np (me, &attr) == 0);
+  TEST_VERIFY_EXIT (pthread_attr_getstack (&attr, &old_stack_addr,
+					    &stack_size) == 0);
 # if _STACK_GROWS_DOWN
     old_stack_addr += stack_size;
 # else
@@ -143,18 +147,12 @@  do_test (void)
   const char *soname = "tst-execstack-mod.so";
 #endif
   void *h = dlopen (soname, RTLD_LAZY);
-  if (h == NULL)
-    {
-      printf ("cannot load: %s\n", dlerror ());
-      return allow_execstack;
-    }
+#if !DEFAULT_RWX_STACK
+  TEST_VERIFY_EXIT (h == NULL);
+#else
+  TEST_VERIFY_EXIT (h != NULL);
 
-  f = dlsym (h, "tryme");
-  if (f == NULL)
-    {
-      printf ("symbol not found: %s\n", dlerror ());
-      return 1;
-    }
+  f = xdlsym (h, "tryme");
 
   /* Test if that really made our stack executable.
      The `tryme' function should crash if not.  */
@@ -163,28 +161,15 @@  do_test (void)
 
   print_maps ();
 
-#if USE_PTHREADS
-  ret = pthread_getattr_np (me, &attr);
-  if (ret)
-    {
-      printf ("after execstack: pthread_getattr_np returned error: %s\n",
-	      strerror (ret));
-      return 1;
-    }
-
-  ret = pthread_attr_getstack (&attr, &new_stack_addr, &stack_size);
-  if (ret)
-    {
-      printf ("after execstack: pthread_attr_getstack returned error: %s\n",
-	      strerror (ret));
-      return 1;
-    }
-
-# if _STACK_GROWS_DOWN
+# if USE_PTHREADS
+  TEST_VERIFY_EXIT (pthread_getattr_np (me, &attr) == 0);
+  TEST_VERIFY_EXIT (pthread_attr_getstack (&attr, &new_stack_addr,
+					    &stack_size) == 0);
+#  if _STACK_GROWS_DOWN
     new_stack_addr += stack_size;
-# else
+#  else
     new_stack_addr -= stack_size;
-# endif
+#  endif
 
   /* It is possible that the dlopen'd module may have been mmapped just below
      the stack.  The stack size is taken as MIN(stack rlimit size, end of last
@@ -194,48 +179,29 @@  do_test (void)
      stacksize and stackaddr respectively.  If the size changes due to the
      above, then both stacksize and stackaddr can change, but the stack bottom
      should remain the same, which is computed as stackaddr + stacksize.  */
-  if (old_stack_addr != new_stack_addr)
-    {
-      printf ("Stack end changed, old: %p, new: %p\n",
-	      old_stack_addr, new_stack_addr);
-      return 1;
-    }
+  TEST_VERIFY_EXIT (old_stack_addr == new_stack_addr);
   printf ("Stack address remains the same: %p\n", old_stack_addr);
-#endif
+# endif
 
   /* Test that growing the stack region gets new executable pages too.  */
   deeper ((void (*) (void)) f);
 
   print_maps ();
 
-#if USE_PTHREADS
+# if USE_PTHREADS
   /* Test that a fresh thread now gets an executable stack.  */
-  {
-    pthread_t th;
-    int rc = pthread_create (&th, NULL, &tryme_thread, f);
-    if (rc)
-      error (1, rc, "pthread_create");
-  }
+  xpthread_create (NULL, &tryme_thread, f);
 
   puts ("threads go");
   /* The existing threads' stacks should have been changed.
      Let them run to test it.  */
-  pthread_barrier_wait (&go_barrier);
+  xpthread_barrier_wait (&go_barrier);
 
   pthread_exit ((void *) (long int) (! allow_execstack));
+# endif
 #endif
 
   return ! allow_execstack;
 }
 
-static void
-deeper (void (*f) (void))
-{
-  char stack[1100 * 1024];
-  explicit_bzero (stack, sizeof stack);
-  (*f) ();
-  memfrob (stack, sizeof stack);
-}
-
-
 #include <support/test-driver.c>
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index d9adb5856c..9662b43afe 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -448,25 +448,6 @@  allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
 
 	  lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
 
-
-	  /* There might have been a race.  Another thread might have
-	     caused the stacks to get exec permission while this new
-	     stack was prepared.  Detect if this was possible and
-	     change the permission if necessary.  */
-	  if (__builtin_expect ((GL(dl_stack_flags) & PF_X) != 0
-				&& (prot & PROT_EXEC) == 0, 0))
-	    {
-	      int err = __nptl_change_stack_perm (pd);
-	      if (err != 0)
-		{
-		  /* Free the stack memory we just allocated.  */
-		  (void) __munmap (mem, size);
-
-		  return err;
-		}
-	    }
-
-
 	  /* Note that all of the stack and the thread descriptor is
 	     zeroed.  This means we do not have to initialize fields
 	     with initial value zero.  This is specifically true for
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index 91447a5e77..b897da7e7b 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -413,13 +413,6 @@  struct rtld_global
 #endif
 #include <dl-procruntime.c>
 
-#if !PTHREAD_IN_LIBC
-  /* If loading a shared object requires that we make the stack executable
-     when it was not, we do it by calling this function.
-     It returns an errno code or zero on success.  */
-  EXTERN int (*_dl_make_stack_executable_hook) (void **);
-#endif
-
   /* Prevailing state of the stack, PF_X indicating it's executable.  */
   EXTERN ElfW(Word) _dl_stack_flags;
 
@@ -716,17 +709,10 @@  extern const ElfW(Phdr) *_dl_phdr;
 extern size_t _dl_phnum;
 #endif
 
-#if PTHREAD_IN_LIBC
-/* This function changes the permissions of all stacks (not just those
-   of the main stack).  */
-int _dl_make_stacks_executable (void **stack_endp) attribute_hidden;
-#else
-/* This is the initial value of GL(dl_make_stack_executable_hook).
-   A threads library can change it.  The ld.so implementation changes
-   the permissions of the main stack only.  */
-extern int _dl_make_stack_executable (void **stack_endp);
-rtld_hidden_proto (_dl_make_stack_executable)
-#endif
+/* This function changes the permission of the memory region pointed
+   by STACK_ENDP to executable and update the internal memory protection
+   flags for future thread stack creation.  */
+int _dl_make_stack_executable (void **stack_endp) attribute_hidden;
 
 /* Variable pointing to the end of the stack (or close to it).  This value
    must be constant over the runtime of the application.  Some programs
diff --git a/sysdeps/mach/hurd/dl-execstack.c b/sysdeps/mach/hurd/dl-execstack.c
index 31371bc6e3..0222430131 100644
--- a/sysdeps/mach/hurd/dl-execstack.c
+++ b/sysdeps/mach/hurd/dl-execstack.c
@@ -47,4 +47,3 @@  _dl_make_stack_executable (void **stack_endp)
   return ENOSYS;
 #endif
 }
-rtld_hidden_def (_dl_make_stack_executable)
diff --git a/sysdeps/nptl/pthreadP.h b/sysdeps/nptl/pthreadP.h
index c2db165052..a8e09bf754 100644
--- a/sysdeps/nptl/pthreadP.h
+++ b/sysdeps/nptl/pthreadP.h
@@ -289,12 +289,6 @@  extern _Noreturn void __syscall_do_cancel (void) attribute_hidden;
 extern void __nptl_free_tcb (struct pthread *pd);
 libc_hidden_proto (__nptl_free_tcb)
 
-/* Change the permissions of a thread stack.  Called from
-   _dl_make_stacks_executable and pthread_create.  */
-int
-__nptl_change_stack_perm (struct pthread *pd);
-rtld_hidden_proto (__nptl_change_stack_perm)
-
 /* longjmp handling.  */
 extern void __pthread_cleanup_upto (__jmp_buf target, char *targetframe);
 libc_hidden_proto (__pthread_cleanup_upto)
diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions
index 213ff5f1fe..55d565545a 100644
--- a/sysdeps/unix/sysv/linux/Versions
+++ b/sysdeps/unix/sysv/linux/Versions
@@ -360,7 +360,4 @@  ld {
     __rseq_offset;
     __rseq_size;
   }
-  GLIBC_PRIVATE {
-    __nptl_change_stack_perm;
-  }
 }
diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c
index b986898598..68db6737f0 100644
--- a/sysdeps/unix/sysv/linux/dl-execstack.c
+++ b/sysdeps/unix/sysv/linux/dl-execstack.c
@@ -16,19 +16,10 @@ 
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
 #include <ldsodefs.h>
-#include <libintl.h>
-#include <list.h>
-#include <pthreadP.h>
-#include <stackinfo.h>
-#include <stdbool.h>
-#include <sys/mman.h>
-#include <sysdep.h>
-#include <unistd.h>
 
-static int
-make_main_stack_executable (void **stack_endp)
+int
+_dl_make_stack_executable (void **stack_endp)
 {
   /* This gives us the highest/lowest page that needs to be changed.  */
   uintptr_t page = ((uintptr_t) *stack_endp
@@ -52,57 +43,3 @@  make_main_stack_executable (void **stack_endp)
 
   return 0;
 }
-
-int
-_dl_make_stacks_executable (void **stack_endp)
-{
-  /* First the main thread's stack.  */
-  int err = make_main_stack_executable (stack_endp);
-  if (err != 0)
-    return err;
-
-  lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
-
-  list_t *runp;
-  list_for_each (runp, &GL (dl_stack_used))
-    {
-      err = __nptl_change_stack_perm (list_entry (runp, struct pthread, list));
-      if (err != 0)
-	break;
-    }
-
-  /* Also change the permission for the currently unused stacks.  This
-     might be wasted time but better spend it here than adding a check
-     in the fast path.  */
-  if (err == 0)
-    list_for_each (runp, &GL (dl_stack_cache))
-      {
-	err = __nptl_change_stack_perm (list_entry (runp, struct pthread,
-						    list));
-	if (err != 0)
-	  break;
-      }
-
-  lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
-
-  return err;
-}
-
-int
-__nptl_change_stack_perm (struct pthread *pd)
-{
-#if _STACK_GROWS_DOWN
-  void *stack = pd->stackblock + pd->guardsize;
-  size_t len = pd->stackblock_size - pd->guardsize;
-#elif _STACK_GROWS_UP
-  void *stack = pd->stackblock;
-  size_t len = (uintptr_t) pd - pd->guardsize - (uintptr_t) pd->stackblock;
-#else
-# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
-#endif
-  if (__mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
-    return errno;
-
-  return 0;
-}
-rtld_hidden_def (__nptl_change_stack_perm)
diff --git a/sysdeps/unix/sysv/linux/mips/Makefile b/sysdeps/unix/sysv/linux/mips/Makefile
index d5725c69d8..05ec9150b2 100644
--- a/sysdeps/unix/sysv/linux/mips/Makefile
+++ b/sysdeps/unix/sysv/linux/mips/Makefile
@@ -61,6 +61,7 @@  ifeq ($(subdir),elf)
 # this test is expected to fail.
 ifneq ($(mips-has-gnustack),yes)
 test-xfail-check-execstack = yes
+CFLAGS-tst-execstack.c += -DDEFAULT_RWX_STACK=1
 endif
 endif
 
@@ -68,6 +69,12 @@  ifeq ($(subdir),stdlib)
 gen-as-const-headers += ucontext_i.sym
 endif
 
+ifeq ($(subdir),nptl)
+ifeq ($(mips-force-execstack),yes)
+CFLAGS-tst-execstack-threads.c += -DDEFAULT_RWX_STACK=1
+endif
+endif
+
 ifeq ($(mips-force-execstack),yes)
 CFLAGS-.o += -Wa,-execstack
 CFLAGS-.os += -Wa,-execstack