Feat: pointer validation checks string across multiple pages and handle kernel page faults

src/userprog/syscall.c

@@ -10,9 +10,6 @@
 #include "threads/synch.h"
 #include "userprog/process.h"
 #include "userprog/pagedir.h"
-#ifdef VM
-#include "vm/stackgrowth.h"
-#endif
 #include <stdio.h>
 #include <stdbool.h>
 #include <syscall-nr.h>
@@ -465,17 +462,17 @@ validate_user_pointer (const void *ptr, size_t size, bool check_write)
      valid user virtual memory address. */
   void *last = ptr + size - 1;
   if (!is_user_vaddr (last))
-    thread_exit ();
+    syscall_exit (EXIT_FAILURE);
   ptr = pg_round_down (ptr);
   while (ptr <= last)
     {
       int result;
       /* Check read access to pointer. */
       if ((result = get_user (ptr)) == -1)
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       /* Check write access to pointer (if required). */
       if (check_write && !put_user (ptr, result))
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       ptr += PGSIZE;
     }
 }
@@ -485,18 +482,33 @@ validate_user_pointer (const void *ptr, size_t size, bool check_write)
 static void
 validate_user_string (const char *ptr, bool check_write)
 {
-  while (true)
+  size_t offset = (uintptr_t) ptr % PGSIZE;
+
+  for (;;)
     {
+      void *page = pg_round_down (ptr);
+
+      if (!is_user_vaddr (page))
+        syscall_exit (EXIT_FAILURE);
       if (!is_user_vaddr (ptr))
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       int result;
       if ((result = get_user ((const uint8_t *)ptr)) == -1)
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       if (check_write && !put_user ((uint8_t *)ptr, result))
-        thread_exit ();
-      if (*ptr == '\0')
-        return;
-      ptr++;
+        syscall_exit (EXIT_FAILURE);
+
+      while (offset < PGSIZE)
+      {
+        if (*ptr == '\0')
+          return; /* We reached the end of the string without issues. */
+
+        ptr++;
+        offset++;
+      }
+
+      offset = 0;
+
     }
 }