Re: [PATCH] x86/uaccess: small optimization in unsafe_copy_to_user()

From: Al Viro
Date: Sat Apr 17 2021 - 16:35:30 EST

On Sat, Apr 17, 2021 at 08:30:42PM +0000, Al Viro wrote:

> and that thing is still there. However, it does *NOT* do what it might
> appear to be doing; it ends up with getdents() returning -EINVAL instead.
> What we need is
> buf->error = -EINTR;
> in addition to that return (in all 3 such places). Do you have any problems with
> the following delta?

No, wait - we have non-NULL buf->prev_reclen, so we'll hit
if (buf.prev_reclen) {
struct compat_linux_dirent __user * lastdirent;
lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;

if (put_user(buf.ctx.pos, &lastdirent->d_off))
error = -EFAULT;
error = count - buf.count;
with buf->error completely ignored. Nevermind.