Messages in this thread | | | Date | Sat, 8 Aug 2009 07:20:31 -0400 | From | Jeff Layton <> | Subject | Re: [PATCH 2/4] vfs: explicitly cast s_maxbytes in fiemap_check_ranges |
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On Sat, 8 Aug 2009 00:12:52 +0200 Johannes Weiner <hannes@cmpxchg.org> wrote:
> On Fri, Aug 07, 2009 at 02:57:39PM -0400, Jeff Layton wrote: > > If fiemap_check_ranges is passed a large enough value, then it's > > possible that the value would be cast to a signed value for comparison > > against s_maxbytes when we change it to loff_t. Make sure that doesn't > > happen by explicitly casting s_maxbytes to an unsigned value for the > > purposes of comparison. > > I think this is unneeded, C garuantees that in this case the signed > value will get promoted to an unsigned value, not the other way round. >
After looking at this again, I think you're correct. do_sendfile was actually casting s_maxbytes to a signed value which is why it was broken there.
I can drop this patch if the consensus is to do so. I still think however that it doesn't hurt to do explict casts when comparing signed and unsigned values to remove any potential for ambiguity.
-- Jeff Layton <jlayton@redhat.com>
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