x86/mm: Use lookup_address_in_pgd_attr() in show_fault_oops()

Fix show_fault_oops() to not only look at the leaf PTE for detecting
NX violations, but to use the effective NX value returned by
lookup_address_in_pgd_attr() instead.

Signed-off-by: Juergen Gross <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: jgross1

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",