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Date: Mon, 22 Sep 2014 08:33:54 -0700
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Subject: Re: [PATCH] Fix nasty 32-bit overflow bug in buffer i/o code.
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Anton Altaparmakov <aia21@cam.ac.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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        Hugh Dickins <hughd@google.com>, stable <stable@vger.kernel.org>
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On Mon, Sep 22, 2014 at 8:29 AM, Anton Altaparmakov <aia21@cam.ac.uk> wrote:
>
> You could do "block & ~(sector_t)(size - 1)" instead of "(sector_t)index << sizebits" if you prefer but not sure that is an improvement!

No, it would be even worse. Something like

  block & ~(sector_t)((size >> 9) - 1)

because block is the sector number (ie 512-byte) and size is in bytes.

           Linus