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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 14 Jul 2021 13:16:19 -0700
Message-ID: <CAHk-=wiaGVapioim31weBWs4bnzt7+wdyAx8GNFVgrFCLc-YXg@mail.gmail.com>
Subject: Re: [GIT PULL] configfs fix for Linux 5.14
To:     Christoph Hellwig <hch@infradead.org>,
        Bart Van Assche <bvanassche@acm.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
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On Wed, Jul 14, 2021 at 1:05 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I hope/think that we always end up checking 'pos' in the VFS layer so
> that this isn't a bug in practice

Yeah, we seem to make sure everything is fine in rw_verify_area().

We do allow negative 'pos' things, but only for files marked with
FMODE_UNSIGNED_OFFSET, which is basically just for variations of
/dev/mem and /proc/<pid>/mem that need the whole 64-bit range.

So it _shouldn't_ be an issue here, but the points about just doing
the legible and safe version stands.

               Linus