From c6e8b680148ad6adb9737865593cb78e66ae0bb0 Mon Sep 17 00:00:00 2001
From: CCXXXI <ccxxxi@qq.com>
Date: Mon, 11 Jan 2021 01:51:28 +0800
Subject: [PATCH] fix bug

---
 src/userprog/syscall.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index 9d07b77..07a1e03 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -171,7 +171,7 @@ static bool is_valid_str(const char *str)
     for (char *c = str; *c != '\0';)
     {
         ++c;
-        if (c - str + 2 == PGSIZE || (unsigned)c & PGMASK == 0 && !is_valid_ptr(c))
+        if (c - str + 2 == PGSIZE || !is_valid_ptr(c))
             return false;
     }