Merge tag 'x86-mm-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 mm updates from Ingo Molnar:

 - Fix W^X violation check false-positives in the CPA code
   when running as a Xen PV guest

 - Fix W^X violation warning false-positives in show_fault_oops()

* tag 'x86-mm-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/pat: Fix W^X violation false-positives when running as Xen PV guest
  x86/pat: Restructure _lookup_address_cpa()
  x86/mm: Use lookup_address_in_pgd_attr() in show_fault_oops()
  x86/pat: Introduce lookup_address_in_pgd_attr()

2 files changed, 58 insertions, 17 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index bba4e020dd64..f26ecabc9424 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -514,18 +514,19 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code, unsigned long ad
 
 	if (error_code & X86_PF_INSTR) {
 		unsigned int level;
+		bool nx, rw;
 		pgd_t *pgd;
 		pte_t *pte;
 
 		pgd = __va(read_cr3_pa());
 		pgd += pgd_index(address);
 
-		pte = lookup_address_in_pgd(pgd, address, &level);
+		pte = lookup_address_in_pgd_attr(pgd, address, &level, &nx, &rw);
 
-		if (pte && pte_present(*pte) && !pte_exec(*pte))
+		if (pte && pte_present(*pte) && (!pte_exec(*pte) || nx))
 			pr_crit("kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n",
 				from_kuid(&init_user_ns, current_uid()));
-		if (pte && pte_present(*pte) && pte_exec(*pte) &&
+		if (pte && pte_present(*pte) && pte_exec(*pte) && !nx &&
 				(pgd_flags(*pgd) & _PAGE_USER) &&
 				(__read_cr4() & X86_CR4_SMEP))
 			pr_crit("unable to execute userspace code (SMEP?) (uid: %d)\n",
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index 80c9037ffadf..19fdfbb171ed 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -619,7 +619,8 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long start,
  * Validate 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 pfn, unsigned long npg,
+				  bool nx, bool rw)
 {
 	unsigned long end;
 
@@ -641,6 +642,10 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star
 	if ((pgprot_val(new) & (_PAGE_RW | _PAGE_NX)) != _PAGE_RW)
 		return new;
 
+	/* Non-leaf translation entries can disable writing or execution. */
+	if (!rw || nx)
+		return new;
+
 	end = start + npg * PAGE_SIZE - 1;
 	WARN_ONCE(1, "CPA detected W^X violation: %016llx -> %016llx range: 0x%016lx - 0x%016lx PFN %lx\n",
 		  (unsigned long long)pgprot_val(old),
@@ -657,20 +662,26 @@ static inline pgprot_t verify_rwx(pgprot_t old, pgprot_t new, unsigned long star
 
 /*
  * 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.
+ * Return a pointer to the entry, the level of the mapping, and the effective
+ * NX and RW bits of all page table levels.
  */
-pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
-			     unsigned int *level)
+pte_t *lookup_address_in_pgd_attr(pgd_t *pgd, unsigned long address,
+				  unsigned int *level, bool *nx, bool *rw)
 {
 	p4d_t *p4d;
 	pud_t *pud;
 	pmd_t *pmd;
 
 	*level = PG_LEVEL_NONE;
+	*nx = false;
+	*rw = true;
 
 	if (pgd_none(*pgd))
 		return NULL;
 
+	*nx |= pgd_flags(*pgd) & _PAGE_NX;
+	*rw &= pgd_flags(*pgd) & _PAGE_RW;
+
 	p4d = p4d_offset(pgd, address);
 	if (p4d_none(*p4d))
 		return NULL;
@@ -679,6 +690,9 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
 	if (p4d_leaf(*p4d) || !p4d_present(*p4d))
 		return (pte_t *)p4d;
 
+	*nx |= p4d_flags(*p4d) & _PAGE_NX;
+	*rw &= p4d_flags(*p4d) & _PAGE_RW;
+
 	pud = pud_offset(p4d, address);
 	if (pud_none(*pud))
 		return NULL;
@@ -687,6 +701,9 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
 	if (pud_leaf(*pud) || !pud_present(*pud))
 		return (pte_t *)pud;
 
+	*nx |= pud_flags(*pud) & _PAGE_NX;
+	*rw &= pud_flags(*pud) & _PAGE_RW;
+
 	pmd = pmd_offset(pud, address);
 	if (pmd_none(*pmd))
 		return NULL;
@@ -695,12 +712,27 @@ pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
 	if (pmd_leaf(*pmd) || !pmd_present(*pmd))
 		return (pte_t *)pmd;
 
+	*nx |= pmd_flags(*pmd) & _PAGE_NX;
+	*rw &= pmd_flags(*pmd) & _PAGE_RW;
+
 	*level = PG_LEVEL_4K;
 
 	return pte_offset_kernel(pmd, address);
 }
 
 /*
+ * 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.
+ */
+pte_t *lookup_address_in_pgd(pgd_t *pgd, unsigned long address,
+			     unsigned int *level)
+{
+	bool nx, rw;
+
+	return lookup_address_in_pgd_attr(pgd, address, level, &nx, &rw);
+}
+
+/*
  * Lookup the page table entry for a virtual address. Return a pointer
  * to the entry and the level of the mapping.
  *
@@ -715,13 +747,16 @@ pte_t *lookup_address(unsigned long address, unsigned int *level)
 EXPORT_SYMBOL_GPL(lookup_address);
 
 static pte_t *_lookup_address_cpa(struct cpa_data *cpa, unsigned long address,
-				  unsigned int *level)
+				  unsigned int *level, bool *nx, bool *rw)
 {
-	if (cpa->pgd)
-		return lookup_address_in_pgd(cpa->pgd + pgd_index(address),
-					       address, level);
+	pgd_t *pgd;
+
+	if (!cpa->pgd)
+		pgd = pgd_offset_k(address);
+	else
+		pgd = cpa->pgd + pgd_index(address);
 
-	return lookup_address(address, level);
+	return lookup_address_in_pgd_attr(pgd, address, level, nx, rw);
 }
 
 /*
@@ -849,12 +884,13 @@ static int __should_split_large_page(pte_t *kpte, unsigned long address,
 	pgprot_t old_prot, new_prot, req_prot, chk_prot;
 	pte_t new_pte, *tmp;
 	enum pg_level level;
+	bool nx, rw;
 
 	/*
 	 * Check for races, another CPU might have split this page
 	 * up already:
 	 */
-	tmp = _lookup_address_cpa(cpa, address, &level);
+	tmp = _lookup_address_cpa(cpa, address, &level, &nx, &rw);
 	if (tmp != kpte)
 		return 1;
 
@@ -965,7 +1001,8 @@ 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);
+	new_prot = verify_rwx(old_prot, new_prot, lpaddr, old_pfn, numpages,
+			      nx, rw);
 
 	/*
 	 * If there is a conflict, split the large page.
@@ -1046,6 +1083,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
 	pte_t *pbase = (pte_t *)page_address(base);
 	unsigned int i, level;
 	pgprot_t ref_prot;
+	bool nx, rw;
 	pte_t *tmp;
 
 	spin_lock(&pgd_lock);
@@ -1053,7 +1091,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, unsigned long address,
 	 * Check for races, another CPU might have split this page
 	 * up for us already:
 	 */
-	tmp = _lookup_address_cpa(cpa, address, &level);
+	tmp = _lookup_address_cpa(cpa, address, &level, &nx, &rw);
 	if (tmp != kpte) {
 		spin_unlock(&pgd_lock);
 		return 1;
@@ -1594,10 +1632,11 @@ static int __change_page_attr(struct cpa_data *cpa, int primary)
 	int do_split, err;
 	unsigned int level;
 	pte_t *kpte, old_pte;
+	bool nx, rw;
 
 	address = __cpa_addr(cpa, cpa->curpage);
 repeat:
-	kpte = _lookup_address_cpa(cpa, address, &level);
+	kpte = _lookup_address_cpa(cpa, address, &level, &nx, &rw);
 	if (!kpte)
 		return __cpa_process_fault(cpa, address, primary);
 
@@ -1619,7 +1658,8 @@ repeat:
 		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 = verify_rwx(old_prot, new_prot, address, pfn, 1,
+				      nx, rw);
 
 		new_prot = pgprot_clear_protnone_bits(new_prot);