NaCl: Fix off-by-one in getcwd() syscall emulation.

sysdeps/nacl/sysdep.h

Index: sysdeps/nacl/sysdep.h
diff --git a/sysdeps/nacl/sysdep.h b/sysdeps/nacl/sysdep.h
index 2e2b8b09bd908bccc50e9d42a2845249896d1a2c..cc47fab815036662c59b6146ec83302045931db9 100644
--- a/sysdeps/nacl/sysdep.h
+++ b/sysdeps/nacl/sysdep.h
@@ -598,8 +598,8 @@ INTERNAL_SYSCALL_getcwd_2 (int *err, char *buf, size_t size)
   if (*err) {
     return 0;
   }
-  for (len = 0; len < size && buf[len] != '\0'; ++len);
-  return len;
+  for (len = 0; buf[len] != '\0'; ++len);

[Roland McGrath, 2014/12/08 20:56:48]

Why is it safe to presume it's terminated and not check size?
Either way, this should just call strlen or __strnlen rather than using a loop.

[Sam Clegg, 2014/12/08 21:10:29]

Because the __nacl_irt_getcwd will fail if it couldn't fit the enture
null terminiated string in buf.  So we could have returned already
above in this case.

I will try strlen.  I was assuming whoever wrote this has a good reason
for using a loop.

[Sam Clegg, 2014/12/08 22:38:39]

Ok. Done.  Although in the case when __nacl_irt_getcwd violates its contract and
doesn't NULL terminate there isn't much we can do here.. somebody further up the
callstack is going to have hard time.

+  return len + 1;
 }
 
 __extern_always_inline gid_t