Messages in this thread | | | Subject | Re: [PATCH] Fix nasty 32-bit overflow bug in buffer i/o code. | From | Anton Altaparmakov <> | Date | Mon, 22 Sep 2014 16:29:56 +0100 |
| |
Hi Linus,
On 22 Sep 2014, at 16:18, Linus Torvalds <torvalds@linux-foundation.org> wrote: > On Sun, Sep 21, 2014 at 5:53 PM, Anton Altaparmakov <aia21@cam.ac.uk> wrote: >> >> This patch fixes this issue by type casting "index" to sector_t before >> doing the left shift. > > Ugh. Does the simpler patch to just pass in "block" work as well?
That doesn't work because nothing rounds down "block" to the first block in the page and init_page_buffers() requires "block" to be the first block in the page.
The shift right followed by shift left achieves the "rounding down" required.
You could do "block & ~(sector_t)(size - 1)" instead of "(sector_t)index << sizebits" if you prefer but not sure that is an improvement!
Best regards,
Anton
> Linus > <patch.diff>
-- Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) University of Cambridge Information Services, Roger Needham Building 7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK
| |