[PATCH] undo do_readv_writev() behavior change

Bugme bug 4326: http://bugme.osdl.org/show_bug.cgi?id=4326 reports:

executing the systemcall readv with Bad argument
->len == -1) it gives out error EFAULT instead of EINVAL 
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/read_write.c

@@ -467,10 +467,10 @@ static ssize_t do_readv_writev(int type, struct file *file,
 		void __user *buf = iov[seg].iov_base;
 		ssize_t len = (ssize_t)iov[seg].iov_len;
 
-		if (unlikely(!access_ok(vrfy_dir(type), buf, len)))
-			goto Efault;
 		if (len < 0)	/* size_t not fitting an ssize_t .. */
 			goto out;
+		if (unlikely(!access_ok(vrfy_dir(type), buf, len)))
+			goto Efault;
 		tot_len += len;
 		if ((ssize_t)tot_len < 0) /* maths overflow on the ssize_t */
 			goto out;