Fix the initial idle tasks environment

- User mode allocator was used for setting up the environment. This
  works in flat mode and probably in protected mode as well, as there
  is always a a single user allocator present
- This does not work in kernel mode, where each user task has its own
  heap allocator. Also, when the idle tasks environment is being set,
  no allocator is ready and the system crashes at once.

Fix this by using the group allocators instead:
- Idle task is a kernel task, so its group is privileged
- Add group_realloc
- Use the group_malloc/realloc functions instead of kumm_malloc

include/nuttx/kmalloc.h

@@ -123,6 +123,11 @@ extern "C"
 
 FAR void *group_malloc(FAR struct task_group_s *group, size_t nbytes);
 
+/* Functions defined in group/group_realloc.c *******************************/
+
+FAR void *group_realloc(FAR struct task_group_s *group, FAR void *oldmem,
+                        size_t newsize);
+
 /* Functions defined in group/group_zalloc.c ********************************/
 
 FAR void *group_zalloc(FAR struct task_group_s *group, size_t nbytes);
@@ -136,9 +141,10 @@ void group_free(FAR struct task_group_s *group, FAR void *mem);
    * in privileges.
    */
 
-#  define group_malloc(g,n) kumm_malloc(n)
-#  define group_zalloc(g,n) kumm_zalloc(n)
-#  define group_free(g,m)   kumm_free(m)
+#  define group_malloc(g,n)      kumm_malloc(n)
+#  define group_realloc(g,p,s)   kumm_realloc((p),(s))
+#  define group_zalloc(g,n)      kumm_zalloc(n)
+#  define group_free(g,m)        kumm_free(m)
 
 #endif
 

sched/environ/env_dup.c

@@ -94,7 +94,7 @@ int env_dup(FAR struct task_group_s *group)
         {
           /* There is an environment, duplicate it */
 
-          envp = (FAR char *)kumm_malloc(envlen);
+          envp = (FAR char *)group_malloc(ptcb->group, envlen);
           if (envp == NULL)
             {
               /* The parent's environment can not be inherited due to a

sched/environ/env_release.c

@@ -69,7 +69,7 @@ void env_release(FAR struct task_group_s *group)
     {
       /* Free the environment */
 
-      kumm_free(group->tg_envp);
+      group_free(group, group->tg_envp);
     }
 
   /* In any event, make sure that all environment-related variables in the

sched/environ/env_setenv.c

@@ -145,7 +145,7 @@ int setenv(FAR const char *name, FAR const char *value, int overwrite)
   if (group->tg_envp)
     {
       newsize = group->tg_envsize + varlen;
-      newenvp = (FAR char *)kumm_realloc(group->tg_envp, newsize);
+      newenvp = (FAR char *)group_realloc(group, group->tg_envp, newsize);
       if (!newenvp)
         {
           ret = ENOMEM;
@@ -157,7 +157,7 @@ int setenv(FAR const char *name, FAR const char *value, int overwrite)
   else
     {
       newsize = varlen;
-      newenvp = (FAR char *)kumm_malloc(varlen);
+      newenvp = (FAR char *)group_malloc(group, varlen);
       if (!newenvp)
         {
           ret = ENOMEM;

sched/environ/env_unsetenv.c

@@ -86,7 +86,7 @@ int unsetenv(FAR const char *name)
 
           if (group->tg_envp != NULL)
             {
-              kumm_free(group->tg_envp);
+              group_free(group, group->tg_envp);
               group->tg_envp = NULL;
             }
 
@@ -96,7 +96,9 @@ int unsetenv(FAR const char *name)
         {
           /* Reallocate the environment to reclaim a little memory */
 
-          newenvp = (FAR char *)kumm_realloc(group->tg_envp, newsize);
+          newenvp = (FAR char *)group_realloc(group, group->tg_envp,
+                                              newsize);
+
           if (newenvp == NULL)
             {
               set_errno(ENOMEM);

sched/group/Make.defs

@@ -50,7 +50,7 @@ CSRCS += group_exitinfo.c
 endif
 
 ifneq ($(CONFIG_BUILD_FLAT),y)
-CSRCS += group_malloc.c group_zalloc.c group_free.c
+CSRCS += group_malloc.c group_realloc.c group_zalloc.c group_free.c
 endif
 
 # Include group build support

sched/group/group_realloc.c

@@ -0,0 +1,83 @@
+/****************************************************************************
+ * sched/group/group_realloc.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <sys/types.h>
+
+#include <assert.h>
+
+#include <nuttx/sched.h>
+#include <nuttx/kmalloc.h>
+
+#include "sched/sched.h"
+#include "group/group.h"
+
+#ifdef CONFIG_MM_KERNEL_HEAP
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: group_realloc
+ *
+ * Description:
+ *   Re-allocate memory appropriate for the group type.  If the memory is
+ *   part of a privileged group, then it should be allocated so that it
+ *   is only accessible by privileged code;  Otherwise, it is a user mode
+ *   group and must be allocated so that it accessible by unprivileged
+ *   code.
+ *
+ ****************************************************************************/
+
+FAR void *group_realloc(FAR struct task_group_s *group, FAR void *oldmem,
+                        size_t newsize)
+{
+  /* A NULL group pointer means the current group */
+
+  if (group == NULL)
+    {
+      FAR struct tcb_s *tcb = this_task();
+      DEBUGASSERT(tcb && tcb->group);
+      group = tcb->group;
+    }
+
+  /* Check the group type */
+
+  if ((group->tg_flags & GROUP_FLAG_PRIVILEGED) != 0)
+    {
+      /* It is a privileged group... use the kernel mode memory allocator */
+
+      return kmm_realloc(oldmem, newsize);
+    }
+  else
+    {
+      /* This is an unprivileged group... use the user mode memory
+       * allocator.
+       */
+
+      return kumm_realloc(oldmem, newsize);
+    }
+}
+
+#endif /* CONFIG_MM_KERNEL_HEAP */

sched/init/nx_start.c

@@ -558,7 +558,8 @@ void nx_start(void)
        */
 
       group_initialize(&g_idletcb[i]);
-      g_idletcb[i].cmn.group->tg_flags = GROUP_FLAG_NOCLDWAIT;
+      g_idletcb[i].cmn.group->tg_flags = GROUP_FLAG_NOCLDWAIT |
+                                         GROUP_FLAG_PRIVILEGED;
     }
 
   g_lastpid = CONFIG_SMP_NCPUS - 1;