[RFC PATCH 5/5] UM:Prevent write to read-only pages :text, PLT/GOT tables from another process

[Lev Olshvang <levonshe@gmail.com>]

Signed-off-by: Lev Olshvang <levonshe@gmail.com>
---
 arch/um/include/asm/mmu_context.h | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/um/include/asm/mmu_context.h b/arch/um/include/asm/mmu_context.h
index b4deb1bfbb68..2de21d52bd60 100644
--- a/arch/um/include/asm/mmu_context.h
+++ b/arch/um/include/asm/mmu_context.h
@@ -1,5 +1,5 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-/*
+/*
  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  */

@@ -28,6 +28,11 @@ static inline void arch_unmap(struct mm_struct *mm,
 static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
 		bool write, bool execute, bool foreign)
 {
+	#ifdef CONFIG_PROTECT_READONLY_USER_MEMORY
+	/* Forbid write to PROT_READ pages of foreign process */
+	if (write && foreign && (!(vma->vm_flags & VM_WRITE)))
+	return false;
+	#endif
 	/* by default, allow everything */
 	return true;
 }
@@ -52,7 +57,7 @@ static inline void activate_mm(struct mm_struct *old, struct mm_struct *new)
 	up_write(&new->mmap_sem);
 }

-static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
+static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 			     struct task_struct *tsk)
 {
 	unsigned cpu = smp_processor_id();
@@ -65,7 +70,7 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	}
 }

-static inline void enter_lazy_tlb(struct mm_struct *mm,
+static inline void enter_lazy_tlb(struct mm_struct *mm,
 				  struct task_struct *tsk)
 {
 }
--
2.17.1