Commit 652c5bf3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Dave Hansen
Browse files

x86/mm: Refuse W^X violations 



x86 has STRICT_*_RWX, but not even a warning when someone violates it.

Add this warning and fully refuse the transition.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/YwySW3ROc21hN7g9@hirez.programming.kicks-ass.net
parent 86af8230

arch/x86/mm/pat/set_memory.c

+32 −0
Original line number Diff line number Diff line
@@ -579,6 +579,33 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long start, 
	return __pgprot(pgprot_val(prot) & ~forbidden);

}



/*

 * Validate and enforce strict W^X semantics.

 */

static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long start,

				  unsigned long pfn, unsigned long npg)

{

	unsigned long end;



	if (!cpu_feature_enabled(X86_FEATURE_NX))

		return new;



	if (!((pgprot_val(old) ^ pgprot_val(new)) & (_PAGE_RW | _PAGE_NX)))

		return new;



	if ((pgprot_val(new) & (_PAGE_RW | _PAGE_NX)) != _PAGE_RW)

		return new;



	end = start + npg * PAGE_SIZE - 1;

	WARN_ONCE(1, "CPA refuse W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n",

		  (unsigned long long)pgprot_val(old),

		  (unsigned long long)pgprot_val(new),

		  start, end, pfn);



	/* refuse the transition into WX */

	return old;

}



/*

 * Lookup the page table entry for a virtual address in a specific pgd.

 * Return a pointer to the entry and the level of the mapping.
@@ -885,6 +912,8 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address, 
	new_prot = static_protections(req_prot, lpaddr, old_pfn, numpages,

				      psize, CPA_DETECT);



	new_prot = verify_rwx(old_prot, new_prot, lpaddr, old_pfn, numpages);



	/*

	 * If there is a conflict, split the large page.

	 *
@@ -1525,6 +1554,7 @@ static int __change_page_attr(struct cpa_data *cpa, int primary) 


	if (level == PG_LEVEL_4K) {

		pte_t new_pte;

		pgprot_t old_prot = pte_pgprot(old_pte);

		pgprot_t new_prot = pte_pgprot(old_pte);

		unsigned long pfn = pte_pfn(old_pte);
@@ -1536,6 +1566,8 @@ static int __change_page_attr(struct cpa_data *cpa, int primary) 
		new_prot = static_protections(new_prot, address, pfn, 1, 0,

					      CPA_PROTECT);



		new_prot = verify_rwx(old_prot, new_prot, address, pfn, 1);



		new_prot = pgprot_clear_protnone_bits(new_prot);



		/*