From 5683afd1adee798a9288c7d01afc8029c65fe94c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gustav=20S=C3=B6rn=C3=A4s?= <gustav@sornas.net>
Date: Sun, 14 Mar 2021 12:59:00 +0100
Subject: check stack pointer

---
 src/userprog/build/fail |  2 --
 src/userprog/syscall.c  | 29 +++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)

(limited to 'src')

diff --git a/src/userprog/build/fail b/src/userprog/build/fail
index d20593f..fc47d60 100644
--- a/src/userprog/build/fail
+++ b/src/userprog/build/fail
@@ -1,4 +1,3 @@
-FAIL tests/userprog/sc-bad-sp
 FAIL tests/userprog/sc-bad-arg
 FAIL tests/userprog/create-null
 FAIL tests/userprog/create-bad-ptr
@@ -8,4 +7,3 @@ FAIL tests/userprog/read-bad-ptr
 FAIL tests/userprog/write-bad-ptr
 FAIL tests/userprog/exec-bad-ptr
 FAIL tests/userprog/wait-twice
-FAIL tests/userprog/wait-killed
diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index 52526aa..a699784 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -9,9 +9,11 @@
 #include "filesys/filesys.h"
 #include "filesys/off_t.h"
 #include "lib/pid_t.h"
+#include "userprog/pagedir.h"
 #include "userprog/process.h"
 #include "threads/init.h"
 #include "threads/malloc.h"
+#include "threads/vaddr.h"
 
 static void syscall_handler (struct intr_frame *);
 
@@ -162,13 +164,40 @@ exec (const char *file_name)
   return process_execute (file_name);
 }
 
+static bool
+ptr_is_valid (const void *ptr)
+{
+  // uintptr_t ptr = _ptr;
+  if (!is_user_vaddr (ptr))
+    return false;
+
+  struct thread *t = thread_current ();
+
+  if (pagedir_get_page (t->pagedir, ptr) == NULL)
+    return false;
+
+  return true;
+}
+
 // cast to TYPE and deref argument N from f->esp
 #define INTR_ESP(N, TYPE) *(TYPE *)(f->esp+(4*(N)))
 
+#define CHECK_ESP_AND_MAYBE_EXIT(N)          \
+  do {                                       \
+    if (!ptr_is_valid ((f->esp+(4*(N))))) {  \
+      exit (-1);                             \
+      return;                                \
+    }                                        \
+  } while (0)
+
+
 static void
 syscall_handler (struct intr_frame *f UNUSED) 
 {
+  // check esp
+  CHECK_ESP_AND_MAYBE_EXIT (0);
   int syscall_number = INTR_ESP (0, int);
+
   switch (syscall_number) {
     case 0:
       // halt
-- 
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