Commit fac84939 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b1d95f4e

arch/x86/mm/pageattr.c

+15 −2
Original line number Diff line number Diff line
@@ -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:

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