check all pointers before dereferencing

3 files changed, 49 insertions, 19 deletions

diff --git a/src/userprog/build/fail b/src/userprog/build/fail
index fc47d60..e69de29 100644
--- a/src/userprog/build/fail
+++ b/src/userprog/build/fail
@@ -1,9 +0,0 @@
-FAIL tests/userprog/sc-bad-arg
-FAIL tests/userprog/create-null
-FAIL tests/userprog/create-bad-ptr
-FAIL tests/userprog/open-null
-FAIL tests/userprog/open-bad-ptr
-FAIL tests/userprog/read-bad-ptr
-FAIL tests/userprog/write-bad-ptr
-FAIL tests/userprog/exec-bad-ptr
-FAIL tests/userprog/wait-twice
diff --git a/src/userprog/process.c b/src/userprog/process.c
index fbf2f50..6170b53 100644
--- a/src/userprog/process.c
+++ b/src/userprog/process.c
@@ -145,6 +145,8 @@ process_wait (tid_t child_tid)
       sema_down (&pc->exit_sema);
       int exit_status = pc->exit_status;
       pc->exit_status = -1;
+      sema_up (&pc->exit_sema);  // a bit of a hack
+                                 // the child is killed so we can read again if we want to
       return exit_status;
     }
   }
diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index 4d2ce7a..e845edb 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -159,9 +159,9 @@ close (int fd_i)
 }
 
 static pid_t
-exec (const char *file_name)
+exec (const char *filename)
 {
-  return process_execute (file_name);
+  return process_execute (filename);
 }
 
 static bool
@@ -199,6 +199,13 @@ syscall_handler (struct intr_frame *f UNUSED)
 
   CHECK_PTR_AND_MAYBE_EXIT (syscall_number);
 
+  char **filename;
+  int *status, *fd_i;
+  off_t *initial_size;
+  tid_t *child_tid;
+  unsigned *size;
+  void **buf;
+  
   switch (*syscall_number) {
     case 0:
       // halt
@@ -206,35 +213,65 @@ syscall_handler (struct intr_frame *f UNUSED)
       break;
     case 1:
       // exit
-      exit (*INTR_ESP (1, int));
+      status = INTR_ESP (1, int);
+      CHECK_PTR_AND_MAYBE_EXIT (status);
+      exit (*status);
       break;
     case 2:
       // exec
-      f->eax = exec (*INTR_ESP (1, char *));
+      filename = INTR_ESP (1, char *);
+      CHECK_PTR_AND_MAYBE_EXIT (filename);
+      CHECK_PTR_AND_MAYBE_EXIT (*filename);
+      f->eax = exec (*filename);
       break;
     case 3:
       // wait
-      f->eax = wait (*INTR_ESP (1, tid_t));
+      child_tid = INTR_ESP (1, tid_t);
+      CHECK_PTR_AND_MAYBE_EXIT (child_tid);
+      f->eax = wait (*child_tid);
       break;
     case 4:
       // create
-      f->eax = create (*INTR_ESP (1, char *), *INTR_ESP (2, off_t));
+      filename = INTR_ESP (1, char *);
+      initial_size = INTR_ESP (2, off_t);
+      CHECK_PTR_AND_MAYBE_EXIT (filename);
+      CHECK_PTR_AND_MAYBE_EXIT (*filename);
+      CHECK_PTR_AND_MAYBE_EXIT (initial_size);
+      f->eax = create (*filename, *initial_size);
       break;
     case 6:
       // open
-      f->eax = open (*INTR_ESP (1, char *));
+      filename = INTR_ESP (1, char *);
+      CHECK_PTR_AND_MAYBE_EXIT (filename);
+      CHECK_PTR_AND_MAYBE_EXIT (*filename);
+      f->eax = open (*filename);
       break;
     case 8:
       // read
-      f->eax = read (*INTR_ESP (1, int), *INTR_ESP (2, void *), *INTR_ESP (3, unsigned));
+      fd_i = INTR_ESP (1, int);
+      buf = INTR_ESP (2, void *);
+      size = INTR_ESP (3, unsigned);
+      CHECK_PTR_AND_MAYBE_EXIT (fd_i);
+      CHECK_PTR_AND_MAYBE_EXIT (buf);
+      CHECK_PTR_AND_MAYBE_EXIT (*buf);
+      CHECK_PTR_AND_MAYBE_EXIT (size);
+      f->eax = read (*fd_i, *buf, *size);
       break;
     case 9:
       // write
-      f->eax = write (*INTR_ESP (1, int), *INTR_ESP (2, const void *), *INTR_ESP (3, unsigned));
+      fd_i = INTR_ESP (1, int);
+      buf = INTR_ESP (2, void *);
+      size = INTR_ESP (3, unsigned);
+      CHECK_PTR_AND_MAYBE_EXIT (fd_i);
+      CHECK_PTR_AND_MAYBE_EXIT (buf);
+      CHECK_PTR_AND_MAYBE_EXIT (*buf);
+      CHECK_PTR_AND_MAYBE_EXIT (size);
+      f->eax = write (*fd_i, *buf, *size);
       break;
     case 12:
       // close
-      close (*INTR_ESP (1, int));
+      fd_i = INTR_ESP (1, int);
+      close (*fd_i);
       break;
     default:
       printf ("kernel: unknown syscall '%d'\n", *syscall_number);