[PATCH] readv/writev syscalls are not checked by lsm

it seems that readv(2)/writev(2) syscalls do not call
file_permission callback. Looks like this is overlook.

I have filled the issue into redhat bugzilla as
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=169433
and got the recommendation to post this on lsm mailing list.

The following trivial patch solves the problem.
Signed-off-by: NKostik Belousov <kostikbel@gmail.com>
Signed-off-by: NChris Wright <chrisw@osdl.org>

fs/read_write.c

@@ -497,6 +497,9 @@ static ssize_t do_readv_writev(int type, struct file *file,
 	}
 
 	ret = rw_verify_area(type, file, pos, tot_len);
+	if (ret)
+		goto out;
+	ret = security_file_permission(file, type == READ ? MAY_READ : MAY_WRITE);
 	if (ret)
 		goto out;