On Wed, 2 Apr 2003, Dave McCracken wrote:
> --On Wednesday, April 02, 2003 15:38:45 -0800 Andrew Morton
> <akpm@digeo.com> wrote:
>
> > But:
> >
> > + /* Double check to make sure the pte page hasn't been freed */
> > + if (!pmd_present(*pmd))
> > + goto out_unmap;
> > +
> > ==> munmap, pte page is freed, reallocated for pagecache, someone
> > happens to write the correct value into it.
> >
> > + if (page_to_pfn(page) != pte_pfn(*pte))
> > + goto out_unmap;
> > +
> > + if (addr)
> > + *addr = address;
> > +
>
> Oops. The pmd_present() check should be after the page_to_pfn() !=
> pte_pfn() check.
No, you're forgetting that the case Andrew rightly indicates is
covered by the ptecount check I added to page_convert_anon, and
commented at length there. As I said yesterday, I don't think
this "Double check" on *pmd serves any real purpose as coded
(whereas the earlier "Double check" on *pgd is vital).
Hugh
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This archive was generated by hypermail 2b29 : Mon Apr 07 2003 - 22:00:18 EST