linux-kernel - Re: [PATCH] fortify: Use WARN instead of BUG for now

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Date:   Wed, 26 Jul 2017 10:10:33 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Micay <danielmicay@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fortify: Use WARN instead of BUG for now

On Tue, Jul 25, 2017 at 8:50 PM, Kees Cook <keescook@...omium.org> wrote:
> +
> +void fortify_read_overflow(const char *func)
>  {
> -       pr_emerg("detected buffer overflow in %s\n", name);
> -       BUG();
> +       WARN(1, "detected read beyond size of object passed as 1st parameter in %s\n", func);
>  }

Side note: have you actually checked the code generation of this all?

In particular, do you have any reason to use the out-of-line
functions? Our WARN() code isn't horrible, and isn't likely to be
noticeably worse than your own explicit out-of-lining. And you'd get
the "unlikely()" for free, so you'll possibly get smaller code that
runs better too.

And it would even *look* better. This:

        if (p_size < size)
               fortify_read_overflow(__func__);

would become

       WARN(p_size < size, "kmemdup size overflow");

or something.

             Linus