Re: [PATCH] add return value checking of get_user() inset_vesa_blanking()

[Andrew Morton]

On Tue, 21 Nov 2006 14:15:28 +0900
Yoichi Yuasa <yoichi_yuasa@xxxxxxxxxxxxxx> wrote:

> Hi,
> 
> This patch has added return value checking of get_user() in set_vesa_blanking().
> 
> Yoichi
> 
> Signed-off-by: Yoichi Yuasa <yoichi_yuasa@xxxxxxxxxxxxxx>
>  
> diff -pruN -X generic/Documentation/dontdiff generic-orig/drivers/char/vt.c generic/drivers/char/vt.c
> --- generic-orig/drivers/char/vt.c	2006-11-21 10:23:39.409667250 +0900
> +++ generic/drivers/char/vt.c	2006-11-21 10:11:48.037209250 +0900
> @@ -3318,9 +3318,10 @@ postcore_initcall(vtconsole_class_init);
>  
>  static void set_vesa_blanking(char __user *p)
>  {
> -    unsigned int mode;
> -    get_user(mode, p + 1);
> -    vesa_blank_mode = (mode < 4) ? mode : 0;
> +	unsigned int mode;
> +
> +	if (!get_user(mode, p + 1))
> +		vesa_blank_mode = (mode < 4) ? mode : 0;
>  }
>  
>  void do_blank_screen(int entering_gfx)

How about we go all the way?

diff -puN drivers/char/vt.c~add-return-value-checking-of-get_user-in drivers/char/vt.c
--- a/drivers/char/vt.c~add-return-value-checking-of-get_user-in
+++ a/drivers/char/vt.c
@@ -152,7 +152,7 @@ static void gotoxy(struct vc_data *vc, i
 static void save_cur(struct vc_data *vc);
 static void reset_terminal(struct vc_data *vc, int do_clear);
 static void con_flush_chars(struct tty_struct *tty);
-static void set_vesa_blanking(char __user *p);
+static int set_vesa_blanking(char __user *p);
 static void set_cursor(struct vc_data *vc);
 static void hide_cursor(struct vc_data *vc);
 static void console_callback(void *ignored);
@@ -2369,7 +2369,7 @@ int tioclinux(struct tty_struct *tty, un
 			ret = __put_user(data, p);
 			break;
 		case TIOCL_SETVESABLANK:
-			set_vesa_blanking(p);
+			ret = set_vesa_blanking(p);
 			break;
 		case TIOCL_GETKMSGREDIRECT:
 			data = kmsg_redirect;
@@ -3315,9 +3315,13 @@ postcore_initcall(vtconsole_class_init);
 
 static void set_vesa_blanking(char __user *p)
 {
-    unsigned int mode;
-    get_user(mode, p + 1);
-    vesa_blank_mode = (mode < 4) ? mode : 0;
+	unsigned int mode;
+
+	if (get_user(mode, p + 1))
+		return -EFAULT;
+
+	vesa_blank_mode = (mode < 4) ? mode : 0;
+	return 0;
 }
 
 void do_blank_screen(int entering_gfx)
_

-
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