kernel: Fix execve filename access on ARM64

kernel/util.c

@@ -0,0 +1,76 @@
+#include <linux/mm.h>
+#include <linux/pgtable.h>
+#include <linux/printk.h>
+#include <asm/current.h>
+
+#include "util.h"
+
+bool try_set_access_flag(unsigned long addr)
+{
+#ifdef CONFIG_ARM64
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+	pte_t *ptep, pte;
+	spinlock_t *ptl;
+	bool ret = false;
+
+	if (!mm)
+		return false;
+
+	if (!mmap_read_trylock(mm))
+		return false;
+
+	vma = find_vma(mm, addr);
+	if (!vma || addr < vma->vm_start)
+		goto out_unlock;
+
+	pgd = pgd_offset(mm, addr);
+	if (!pgd_present(*pgd))
+		goto out_unlock;
+
+	p4d = p4d_offset(pgd, addr);
+	if (!p4d_present(*p4d))
+		goto out_unlock;
+
+	pud = pud_offset(p4d, addr);
+	if (!pud_present(*pud))
+		goto out_unlock;
+
+	pmd = pmd_offset(pud, addr);
+	if (!pmd_present(*pmd))
+		goto out_unlock;
+
+	if (pmd_trans_huge(*pmd))
+		goto out_unlock;
+
+	ptep = pte_offset_map_lock(mm, pmd, addr, &ptl);
+	if (!ptep)
+		goto out_unlock;
+
+	pte = *ptep;
+
+	if (!pte_present(pte))
+		goto out_pte_unlock;
+
+	if (pte_young(pte)) {
+		ret = true;
+		goto out_pte_unlock;
+	}
+
+	ptep_set_access_flags(vma, addr, ptep, pte_mkyoung(pte), 0);
+	pr_info("set AF for addr %lx\n", addr);
+	ret = true;
+
+out_pte_unlock:
+	pte_unmap_unlock(ptep, ptl);
+out_unlock:
+	mmap_read_unlock(mm);
+	return ret;
+#else
+	return false;
+#endif
+}