linux-kernel - Re: [PATCH] Fix nasty 32-bit overflow bug in buffer i/o code.

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Message-ID: <CA+55aFwAdsJ9EWTx3QvMxs2ReTX19Xvd_s7wc+KQ8qnJjg0WDA@mail.gmail.com>
Date:	Mon, 22 Sep 2014 08:33:54 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Anton Altaparmakov <aia21@....ac.uk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Hugh Dickins <hughd@...gle.com>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH] Fix nasty 32-bit overflow bug in buffer i/o code.

On Mon, Sep 22, 2014 at 8:29 AM, Anton Altaparmakov <aia21@....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
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