From: Thomas Gleixner Date: Sat, 9 Feb 2008 22:24:09 +0000 (+0100) Subject: x86: cpa, strict range check in try_preserve_large_page() X-Git-Tag: v2.6.25-rc1~8^2 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fac84939609a683503947f41eb93e1917d026263;p=linux-2.6 x86: cpa, strict range check in try_preserve_large_page() Right now, we check only the first 4k page for static required protections. This does not take overlapping regions into account. So we might end up setting the wrong permissions/protections for other parts of this large page. This can be optimized further, but correctness is the important part. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index e5d29a112d..440210a227 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -253,10 +253,10 @@ static int try_preserve_large_page(pte_t *kpte, unsigned long address, struct cpa_data *cpa) { - unsigned long nextpage_addr, numpages, pmask, psize, flags; + unsigned long nextpage_addr, numpages, pmask, psize, flags, addr; pte_t new_pte, old_pte, *tmp; pgprot_t old_prot, new_prot; - int do_split = 1; + int i, do_split = 1; unsigned int level; spin_lock_irqsave(&pgd_lock, flags); @@ -303,6 +303,19 @@ try_preserve_large_page(pte_t *kpte, unsigned long address, pgprot_val(new_prot) |= pgprot_val(cpa->mask_set); new_prot = static_protections(new_prot, address); + /* + * We need to check the full range, whether + * static_protection() requires a different pgprot for one of + * the pages in the range we try to preserve: + */ + addr = address + PAGE_SIZE; + for (i = 1; i < cpa->numpages; i++, addr += PAGE_SIZE) { + pgprot_t chk_prot = static_protections(new_prot, addr); + + if (pgprot_val(chk_prot) != pgprot_val(new_prot)) + goto out_unlock; + } + /* * If there are no changes, return. maxpages has been updated * above: