linux-kernel - Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

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Date:   Fri, 14 Jul 2017 16:50:29 -0400
From:   Daniel Micay <danielmicay@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Kees Cook <keescook@...omium.org>
Cc:     Dave Jones <davej@...emonkey.org.uk>,
        Anna Schumaker <schumaker.anna@...il.com>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com
Subject: Re: [GIT PULL] Please pull NFS client changes for Linux 4.13

> My initial patch used strlcpy there, because I wasn't aware of strscpy
> before it was suggested:
> 
> http://www.openwall.com/lists/kernel-hardening/2017/05/04/11
> 
> I was wrong to move it to strscpy. It could be switched back to
> strlcpy
> again unless the kernel considers the count parameter to be a
> guarantee
> that could be leveraged in the future. Using the fortified strlen +
> memcpy would provide the improvement that strscpy was meant to provide
> there over strlcpy.

Similarly, the FORTIFY_SOURCE strcat uses strlcat with the assumption
that the count parameter is a limit, not a guarantee for a optimization.
There's only a C implementation and it currently doesn't, but if it's
meant to be a guarantee then the strcat needs to be changed too.

I'll make a fix moving away both from the existing functions.