linux-hardening - Re: [PATCH v6 0/5] Fortify strscpy()

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Date:   Fri, 20 Nov 2020 10:40:38 +0100
From:   Francis Laniel <laniel_francis@...vacyrequired.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-hardening@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, dja@...ens.net, keescook@...omium.org
Subject: Re: [PATCH v6 0/5] Fortify strscpy()

Le vendredi 20 novembre 2020, 02:35:43 CET Andrew Morton a écrit :
> On Thu, 19 Nov 2020 17:49:10 +0100 laniel_francis@...vacyrequired.com wrote:
> > From: Francis Laniel <laniel_francis@...vacyrequired.com>
> > 
> > Hi.
> > 
> > 
> > I hope your families, friends and yourselves are fine.
> 
> Thanks.  You too ;)

Thank you!

> > This patch set answers to this issue:
> > https://github.com/KSPP/linux/issues/46
> 
> I fail to understand what this patchset has to do with that
> one-element-array issue :(

I think I linked another issue totally not related with that one...

> > I based my modifications on top of two patches from Daniel Axtens which
> > modify calls to __builtin_object_size to ensure the true size of char *
> > are returned and not the surrounding structure size.
> > 
> > To sum up, in my first patch I implemented a fortified version of strscpy.
> > This new version ensures the following before calling vanilla strscpy:
> > 1. There is no read overflow because either size is smaller than src
> > length
> > or we shrink size to src length by calling fortified strnlen.
> > 2. There is no write overflow because we either failed during compilation
> > or at runtime by checking that size is smaller than dest size.
> > The second patch brings a new file in LKDTM driver to test this new
> > version. The test ensures the fortified version still returns the same
> > value as the vanilla one while panic'ing when there is a write overflow.
> > The third just corrects some typos in LKDTM related file.
> > 
> > If you see any problem or way to improve the code, feel free to share it.
> 
> Could you please send along a reworked [0/n] cover letter?  Explain in
> your own words, without requiring that readers go off and read web
> pages
> 
> - What problem the patchset solves
> - How it solves it
> - The value of the patchset (to kernel developers or to end-users) so that
> we can understand why it should be merged.
> 
> Thanks.

I will do it, moreover Kees Cook already told me that cover letter should 
suffices itself (e.g. if the issue disappeared on GitHub).
So I will rework the cover letter for the v7!