linux-kernel - Re: [PATCH] lib/string: avoid reading beyond src buffer in strscpy

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Message-ID: <CA+55aFzmhPFPtDtY4ZY6=yCBFizUJJjacmWREyJvt17V_cmTug@mail.gmail.com>
Date:   Tue, 12 Dec 2017 14:42:51 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     David Laight <David.Laight@...lab.com>,
        Kees Cook <keescook@...omium.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eryu Guan <eguan@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Chris Metcalf <cmetcalf@...hip.com>,
        Alexander Potapenko <glider@...gle.com>
Subject: Re: [PATCH] lib/string: avoid reading beyond src buffer in strscpy

On Tue, Dec 12, 2017 at 8:06 AM, Andrey Ryabinin
<aryabinin@...tuozzo.com> wrote:
>
> See for yourself, strscpy() is the only sting function doing this.

No, strnlen_user() definitely does too.

It's just that KASAN doesn't track user pointers.

And the important strlen() in the kernel is the pathname hashing code,
which *definitely* accesses outside the source, but since it can
actually traverse to another page we have that one annotated too (with
load_unaligned_zeropad()).

So no, strscpy() isn't the only one doing it, it is just the only one
that KASAN catches.

            Linus