mm/vma: introduce VM_ACCESS_FLAGS

There are many places where all basic VMA access flags (read, write,
exec) are initialized or checked against as a group.  One such example
is during page fault.  Existing vma_is_accessible() wrapper already
creates the notion of VMA accessibility as a group access permissions.

Hence lets just create VM_ACCESS_FLAGS (VM_READ|VM_WRITE|VM_EXEC) which
will not only reduce code duplication but also extend the VMA
accessibility concept in general.

Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Salter <msalter@redhat.com>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Guan Xuetao <gxt@pku.edu.cn>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Springer <rspringer@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Link: http://lkml.kernel.org/r/1583391014-8170-3-git-send-email-anshuman.khandual@arm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/arm/mm/fault.c

@@ -189,7 +189,7 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
  */
 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 {
-	unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+	unsigned int mask = VM_ACCESS_FLAGS;
 
 	if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
 		mask = VM_WRITE;

arch/arm64/mm/fault.c

@@ -445,7 +445,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr,
 	const struct fault_info *inf;
 	struct mm_struct *mm = current->mm;
 	vm_fault_t fault, major = 0;
-	unsigned long vm_flags = VM_READ | VM_WRITE | VM_EXEC;
+	unsigned long vm_flags = VM_ACCESS_FLAGS;
 	unsigned int mm_flags = FAULT_FLAG_DEFAULT;
 
 	if (kprobe_page_fault(regs, esr))

arch/nds32/mm/fault.c

@@ -79,7 +79,7 @@ void do_page_fault(unsigned long entry, unsigned long addr,
 	struct vm_area_struct *vma;
 	int si_code;
 	vm_fault_t fault;
-	unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+	unsigned int mask = VM_ACCESS_FLAGS;
 	unsigned int flags = FAULT_FLAG_DEFAULT;
 
 	error_code = error_code & (ITYPE_mskINST | ITYPE_mskETYPE);

arch/powerpc/mm/book3s64/pkeys.c

@@ -315,7 +315,7 @@ int __execute_only_pkey(struct mm_struct *mm)
 static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
 {
 	/* Do this check first since the vm_flags should be hot */
-	if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
+	if ((vma->vm_flags & VM_ACCESS_FLAGS) != VM_EXEC)
 		return false;
 
 	return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);

arch/s390/mm/fault.c

@@ -580,7 +580,7 @@ void do_dat_exception(struct pt_regs *regs)
 	int access;
 	vm_fault_t fault;
 
-	access = VM_READ | VM_EXEC | VM_WRITE;
+	access = VM_ACCESS_FLAGS;
 	fault = do_exception(regs, access);
 	if (unlikely(fault))
 		do_fault_error(regs, access, fault);

arch/unicore32/mm/fault.c

@@ -149,7 +149,7 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
  */
 static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
 {
-	unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
+	unsigned int mask = VM_ACCESS_FLAGS;
 
 	if (!(fsr ^ 0x12))	/* write? */
 		mask = VM_WRITE;

arch/x86/mm/pkeys.c

@@ -63,7 +63,7 @@ int __execute_only_pkey(struct mm_struct *mm)
 static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
 {
 	/* Do this check first since the vm_flags should be hot */
-	if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
+	if ((vma->vm_flags & VM_ACCESS_FLAGS) != VM_EXEC)
 		return false;
 	if (vma_pkey(vma) != vma->vm_mm->context.execute_only_pkey)
 		return false;

drivers/staging/gasket/gasket_core.c

@@ -689,7 +689,7 @@ static bool gasket_mmap_has_permissions(struct gasket_dev *gasket_dev,
 
 	/* Make sure that no wrong flags are set. */
 	requested_permissions =
-		(vma->vm_flags & (VM_WRITE | VM_READ | VM_EXEC));
+		(vma->vm_flags & VM_ACCESS_FLAGS);
 	if (requested_permissions & ~(bar_permissions)) {
 		dev_dbg(gasket_dev->dev,
 			"Attempting to map a region with requested permissions 0x%x, but region has permissions 0x%x.\n",

include/linux/mm.h

@@ -369,6 +369,10 @@ extern unsigned int kobjsize(const void *objp);
 
 #define VM_STACK_FLAGS	(VM_STACK | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)
 
+/* VMA basic access permission flags */
+#define VM_ACCESS_FLAGS (VM_READ | VM_WRITE | VM_EXEC)
+
+
 /*
  * Special vmas that are non-mergable, non-mlock()able.
  */
@@ -646,7 +650,7 @@ static inline bool vma_is_foreign(struct vm_area_struct *vma)
 
 static inline bool vma_is_accessible(struct vm_area_struct *vma)
 {
-	return vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC);
+	return vma->vm_flags & VM_ACCESS_FLAGS;
 }
 
 #ifdef CONFIG_SHMEM

mm/mmap.c

@@ -1224,7 +1224,7 @@ static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *
 	return a->vm_end == b->vm_start &&
 		mpol_equal(vma_policy(a), vma_policy(b)) &&
 		a->vm_file == b->vm_file &&
-		!((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
+		!((a->vm_flags ^ b->vm_flags) & ~(VM_ACCESS_FLAGS | VM_SOFTDIRTY)) &&
 		b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
 }
 

mm/mprotect.c

@@ -419,7 +419,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
 	 */
 	if (arch_has_pfn_modify_check() &&
 	    (vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
-	    (newflags & (VM_READ|VM_WRITE|VM_EXEC)) == 0) {
+	    (newflags & VM_ACCESS_FLAGS) == 0) {
 		pgprot_t new_pgprot = vm_get_page_prot(newflags);
 
 		error = walk_page_range(current->mm, start, end,
@@ -598,7 +598,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
 		newflags |= (vma->vm_flags & ~mask_off_old_flags);
 
 		/* newflags >> 4 shift VM_MAY% in place of VM_% */
-		if ((newflags & ~(newflags >> 4)) & (VM_READ | VM_WRITE | VM_EXEC)) {
+		if ((newflags & ~(newflags >> 4)) & VM_ACCESS_FLAGS) {
 			error = -EACCES;
 			goto out;
 		}