[PATCH] x86_64: read_ldt() clear_user() return value checking

Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/ldt.c

@@ -135,6 +135,7 @@ static int read_ldt(void __user * ptr, unsigned long bytecount)
 		return 0;
 	if (bytecount > LDT_ENTRY_SIZE*LDT_ENTRIES)
 		bytecount = LDT_ENTRY_SIZE*LDT_ENTRIES;
+
 	down(&mm->context.sem);
 	size = mm->context.size*LDT_ENTRY_SIZE;
 	if (size > bytecount)
@@ -145,12 +146,17 @@ static int read_ldt(void __user * ptr, unsigned long bytecount)
 		err = -EFAULT;
 	up(&mm->context.sem);
 	if (err < 0)
-	return err;
+		goto error_return;
 	if (size != bytecount) {
 		/* zero-fill the rest */
-		clear_user(ptr+size, bytecount-size);
+		if (clear_user(ptr+size, bytecount-size) != 0) {
+			err = -EFAULT;
+			goto error_return;
+		}
 	}
 	return bytecount;
+error_return:
+	return err;
 }
 
 static int read_default_ldt(void __user * ptr, unsigned long bytecount)