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 <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index e5d29a1..440210a 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -253,10 +253,10 @@
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);
@@ -304,6 +304,19 @@
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:
*/