diff --git a/src/libos/Enclave_config.xml b/src/libos/Enclave_config.xml
index 1473a769..f18079c4 100644
--- a/src/libos/Enclave_config.xml
+++ b/src/libos/Enclave_config.xml
@@ -2,7 +2,7 @@
 <EnclaveConfiguration>
   <ProdID>0</ProdID>
   <ISVSVN>0</ISVSVN>
-  <StackMaxSize>0x400000</StackMaxSize>
+  <StackMaxSize>0x80000</StackMaxSize>
   <HeapMaxSize>0x1000000</HeapMaxSize>
   <TCSNum>8</TCSNum>
   <TCSPolicy>1</TCSPolicy>
diff --git a/src/libos/src/mm.rs b/src/libos/src/mm.rs
index 173efb18..d79cb039 100644
--- a/src/libos/src/mm.rs
+++ b/src/libos/src/mm.rs
@@ -27,9 +27,9 @@ impl MemObj {
         unsafe { memset(mem_ptr, 0 as c_int, mem_size as size_t) };
 
         Ok(MemObj {
-            mem_ptr: mem_ptr,
-            mem_size: mem_size,
-            mem_align: mem_align,
+            mem_ptr,
+            mem_size,
+            mem_align,
         })
     }
 
diff --git a/src/libos/src/process.rs b/src/libos/src/process.rs
index 1936709c..8a98039e 100644
--- a/src/libos/src/process.rs
+++ b/src/libos/src/process.rs
@@ -91,6 +91,17 @@ pub fn set_current(process: &ProcessRef) {
     });
 }
 
+pub fn reset_current() {
+    let mut process_ptr = 0 as *const SgxMutex<Process>;
+    _CURRENT_PROCESS_PTR.with(|cp| {
+        process_ptr = cp.get();
+        cp.set(0 as *const SgxMutex<Process>);
+    });
+
+    // Prevent memory leakage
+    unsafe { drop(Arc::from_raw(process_ptr)); }
+}
+
 pub fn get_current() -> &'static SgxMutex<Process> {
     let mut process_ptr : *const SgxMutex<Process> = 0 as *const SgxMutex<Process>;
     _CURRENT_PROCESS_PTR.with(|cp| {
@@ -124,6 +135,7 @@ pub fn do_wait4(child_pid: u32, exit_code: &mut i32) -> Result<(), &'static str>
             *exit_code = guard.exit_code;
             break;
         }
+        del_from_pid_table(guard.pid);
         drop(guard);
     }
     Ok(())
@@ -133,16 +145,26 @@ pub fn run_task() -> Result<(), &'static str> {
     let new_process : ProcessRef = dequeue_new_process().ok_or("No new process to run")?;
     set_current(&new_process);
 
+    let pid;
     let new_task;
     {
         let guard = new_process.lock().unwrap();
         let process : &Process = &guard;
-        println!("Run process: {:#x?}", process);
+        pid = process.pid;
+        //println!("Run process: {:#x?}", process);
+        println!("Run process (pid = {})", process.pid);
         new_task = &process.task as *const Task
     };
 
     unsafe { do_run_task(new_task as *const Task); }
 
+    // Init process does not have any parent, so it has to release itself
+    if pid == 1 {
+        del_from_pid_table(1);
+    }
+
+    reset_current();
+
     Ok(())
 }
 
@@ -152,6 +174,7 @@ fn open_elf<P: AsRef<Path>>(path: &P) -> io::Result<Vec<u8>> {
 
     let mut elf_buf = Vec::<u8>::new();
     elf_file.read_to_end(&mut elf_buf);
+    drop(elf_file);
     Ok(elf_buf)
 }
 
@@ -251,7 +274,6 @@ impl Process {
 
 impl Drop for Process {
     fn drop(&mut self) {
-        del_from_pid_table(self.pid);
         free_pid(self.pid);
     }
 }
diff --git a/src/libos/src/vma.rs b/src/libos/src/vma.rs
index abc3be9a..684c0c86 100644
--- a/src/libos/src/vma.rs
+++ b/src/libos/src/vma.rs
@@ -141,7 +141,10 @@ pub fn mprotect_batch(vma_list: &[&Vma])
         let size = (vma.mem_end - vma.mem_begin) as size_t;
         let perms = vma.mem_flags.0 as uint64_t;
         let status = unsafe {
-            trts_mprotect(start, size, perms)
+            //TODO: use proper permissions
+            //TODO: reset the permissions when drop VMA
+            //trts_mprotect(start, size, perms)
+            trts_mprotect(start, size, (PERM_R | PERM_W | PERM_X) as uint64_t)
         };
         if (status != sgx_status_t::SGX_SUCCESS) {
             return Err("trts_mprotect failed");
@@ -151,7 +154,7 @@ pub fn mprotect_batch(vma_list: &[&Vma])
 }
 
 
-#[derive(Copy, Clone, Debug, Default)]
+#[derive(Copy, Clone, Debug, Default, PartialEq)]
 pub struct Perms(pub u32);
 
 pub const PERM_R: u32 = 0x1;
diff --git a/test/spawn_and_wait4_raw/main.c b/test/spawn_and_wait4_raw/main.c
index e9417c8b..92ff5417 100644
--- a/test/spawn_and_wait4_raw/main.c
+++ b/test/spawn_and_wait4_raw/main.c
@@ -7,18 +7,23 @@ static void print_ok(void) {
     __rusgx_write(1, success_str_buf, success_str_size);
 }
 
+#define NUM_CHILDREN            100
+
 void _start(void) {
-    int ret = 0;
-    int pid = 0;
+    for (int ci = 0; ci < NUM_CHILDREN; ci++) {
+        int ret = 0;
+        int pid = 0;
 
-    ret = __rusgx_spawn(&pid, "hello_world_raw/bin.encrypted", NULL, NULL);
-    if (ret < 0) { __rusgx_exit(0); }
+        ret = __rusgx_spawn(&pid, "hello_world_raw/bin.encrypted", NULL, NULL);
+        if (ret < 0) { __rusgx_exit(0); }
+        print_ok();
 
-    int status;
-    ret = __rusgx_wait4(pid, &status, 0);
-    if (ret < 0) { __rusgx_exit(0); }
+        int status;
+        ret = __rusgx_wait4(pid, &status, 0);
+        if (ret < 0) { __rusgx_exit(0); }
 
-    print_ok();
+        //print_ok();
+    }
 
     __rusgx_exit(0);
 }