Messages in this thread | | | Date | Thu, 3 Apr 2003 00:59:09 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH 2.5.66-mm2] Fix page_convert_anon locking issues |
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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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