linux-kernel - Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put

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Date:   Sun, 13 Oct 2019 12:22:38 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to unsafe_put_user()

On Sun, Oct 13, 2019 at 12:10 PM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> No arguments re put_user_ex side of things...  Below is a completely
> untested patch for get_user_ex elimination (it seems to build, but that's
> it); in any case, I would really like to see comments from x86 folks
> before it goes anywhere.

Please don't do this:

> +       if (unlikely(__copy_from_user(&sc, usc, sizeof(sc))))
> +               goto Efault;

Why would you use __copy_from_user()? Just don't.

> +       if (unlikely(__copy_from_user(&v, user_vm86,
> +                       offsetof(struct vm86_struct, int_revectored))))

Same here.

There's no excuse for __copy_from_user().

           Linus