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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 26 Jul 2017 10:10:33 -0700
Message-ID: <CA+55aFwrd2qgnU7evM8ssZ5qsygLMG_47jHx9cvHGPagRAdwuQ@mail.gmail.com>
Subject: Re: [PATCH] fortify: Use WARN instead of BUG for now
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Daniel Micay <danielmicay@gmail.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Al Viro <viro@zeniv.linux.org.uk>, David Howells <dhowells@redhat.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Jul 25, 2017 at 8:50 PM, Kees Cook <keescook@chromium.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