fix stack setup

check if name+arguments fits into one page before copying

1 files changed, 9 insertions, 3 deletions

diff --git a/userprog/process.c b/userprog/process.c
index bf1a706..741503b 100644
--- a/userprog/process.c
+++ b/userprog/process.c
@@ -614,11 +614,17 @@ setup_stack (uint32_t **esp, const char *args)
   stack_end = PHYS_BASE - PGSIZE;
   stack_end += 4 + 1;
 
-  /* copy arguments to stack */
+  /* check if arguments fits into our stack */
   argslen = strlen(args);
   if (argslen > 0)
+    argslen += 1; /* add the trailing \0 */
+  namelen = strlen(name) + 1;
+  if (*esp - argslen - namelen <= stack_end)
+    return false;
+
+  /* copy arguments to stack */
+  if (argslen > 0)
     {
-      argslen += 1; /* add the trailing \0 */
       *(char **) esp -= argslen;
       memcpy(*esp, args, argslen);
     }
@@ -628,7 +634,7 @@ setup_stack (uint32_t **esp, const char *args)
   *(char **) esp -= namelen;
   memcpy(*esp, name, namelen);
 
-  /* align our currend address by word-size (thanks to thomas & edy) */
+  /* align our current address by word-size */
   *(char **) esp -= (sizeof(uint32_t) - (PHYS_BASE - *(void **) esp) % sizeof(uint32_t));
 
   /* terminate argv[] array by NULL ptr */