[PATCH 2/2] mm/vma: Introduce VM_ACCESS_FLAGS

From: Anshuman Khandual <hidden>
Date: 2020-03-05 06:51:01
Also in: linux-mm, linux-s390, linuxppc-dev, lkml
Subsystem: arm port, arm64 port (aarch64 architecture), linux for powerpc (32-bit and 64-bit), memory management, memory management - core, memory mapping, s390 architecture, staging subsystem, the rest, x86 architecture (32-bit and 64-bit), x86 mm · Maintainers: Russell King, Catalin Marinas, Will Deacon, Madhavan Srinivasan, Michael Ellerman, Andrew Morton, David Hildenbrand, Liam R. Howlett, Lorenzo Stoakes, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, Greg Kroah-Hartman, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Andy Lutomirski, Peter Zijlstra

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.

Cc: Russell King <linux@armlinux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Mark Salter <redacted>
Cc: Nick Hu <redacted>
CC: Ley Foon Tan <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <redacted>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Guan Xuetao <redacted>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Thomas Gleixner <redacted>
Cc: Rob Springer <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-s390@vger.kernel.org
Cc: devel@driverdev.osuosl.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <redacted>
---
 arch/arm/mm/fault.c                  | 2 +-
 arch/arm64/mm/fault.c                | 2 +-
 arch/nds32/mm/fault.c                | 2 +-
 arch/powerpc/mm/book3s64/pkeys.c     | 2 +-
 arch/s390/mm/fault.c                 | 2 +-
 arch/unicore32/mm/fault.c            | 2 +-
 arch/x86/mm/pkeys.c                  | 2 +-
 drivers/staging/gasket/gasket_core.c | 2 +-
 include/linux/mm.h                   | 6 +++++-
 mm/mmap.c                            | 2 +-
 mm/mprotect.c                        | 4 ++--
 11 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index bd0f4821f7e1..2c71028d9d6b 100644
--- a/arch/arm/mm/fault.c
+++ b/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;

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 85566d32958f..63f31206a12e 100644
--- a/arch/arm64/mm/fault.c
+++ b/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_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 	if (kprobe_page_fault(regs, esr))

diff --git a/arch/nds32/mm/fault.c b/arch/nds32/mm/fault.c
index 906dfb25353c..55387a31bf42 100644
--- a/arch/nds32/mm/fault.c
+++ b/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_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 	error_code = error_code & (ITYPE_mskINST | ITYPE_mskETYPE);

diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 59e0ebbd8036..11fd52b24f68 100644
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/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);

diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index 7b0bb475c166..b2cb3c0d0e1a 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c

@@ -584,7 +584,7 @@ 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);

diff --git a/arch/unicore32/mm/fault.c b/arch/unicore32/mm/fault.c
index 76342de9cf8c..fc27c274d358 100644
--- a/arch/unicore32/mm/fault.c
+++ b/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;

diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index c6f84c0b5d7a..8873ed1438a9 100644
--- a/arch/x86/mm/pkeys.c
+++ b/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;

diff --git a/drivers/staging/gasket/gasket_core.c b/drivers/staging/gasket/gasket_core.c
index be6b50f454b4..81bb7d58dc49 100644
--- a/drivers/staging/gasket/gasket_core.c
+++ b/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 "

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3861524368a4..e89512f1c170 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h

@@ -368,6 +368,10 @@ 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.
  * Note: mm/huge_memory.c VM_NO_THP depends on this definition.

@@ -557,7 +561,7 @@ static inline bool vma_is_anonymous(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

diff --git a/mm/mmap.c b/mm/mmap.c
index 0d295f49b24d..57f74ade19a0 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c

@@ -1221,7 +1221,7 @@ 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);
 }

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 7a8e84f86831..8fbb7e7c08a5 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c

@@ -359,7 +359,7 @@ 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,

@@ -538,7 +538,7 @@ 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;
 		}

-- 
2.20.1


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