Messages in this thread | | | Date | Thu, 17 Aug 2006 10:47:07 +0200 | From | "Jesper Juhl" <> | Subject | Re: 'fbno' possibly used uninitialized in xfs_alloc_ag_vextent_small() |
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On 17/08/06, Nathan Scott <nathans@sgi.com> wrote: > Hi Jesper, > > On Wed, Aug 16, 2006 at 11:27:34PM +0200, Jesper Juhl wrote: > > (Please keep me on Cc since I'm not subscribed to the XFS lists) > > > > The coverity checker found what looks to me like a valid case of > > potentially uninitialized variable use (see below). > > It looks invalid, but its not, once again. To understand why this > isn't a problem requires looking at the xfs_alloc_ag_vextent_small > call sites (there's only two). If (*flen==0) is passed back out, > then the value in *fbno is discarded, always. > > > So basically, if we hit the 'else' branch, then 'fbno' has not been > > initialized and line 1490 will then use that uninitialized variable. > > > > What would prevent that from happening at some time?? > > Nothing. But its not a problem in practice. However, that final > else branch is very much unlikely, so theres no real cost to just > initialising the local fbno to NULLAGBLOCK in that branch, and we > future proof ourselves a bit that way I guess (in case the callers > ever change - pretty unlikely, but we may as well). How does the > patch below look to you? > Looks good to me.
-- Jesper Juhl <jesper.juhl@gmail.com> Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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