[PATCH 1/7] revoke: special mmap handling

[Pekka J Enberg]

From: Pekka Enberg <penberg@xxxxxxxxxxxxxx>

This adds special handling for revoked memory mappings.  We want to
raise SIGBUS when accessing revoked mappings and return ENODEV when
trying to remap with mmap(2).

Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
---
 include/linux/mm.h |    2 ++
 mm/memory.c        |    3 +++
 mm/mmap.c          |   12 ++++++++----
 3 files changed, 13 insertions(+), 4 deletions(-)

Index: uml-2.6/include/linux/mm.h
===================================================================
--- uml-2.6.orig/include/linux/mm.h	2007-03-08 10:24:24.000000000 +0200
+++ uml-2.6/include/linux/mm.h	2007-03-08 10:24:25.000000000 +0200
@@ -170,6 +170,8 @@
 #define VM_INSERTPAGE	0x02000000	/* The vma has had "vm_insert_page()" done on it */
 #define VM_ALWAYSDUMP	0x04000000	/* Always include in core dumps */
 
+#define VM_REVOKED	0x04000000	/* Mapping has been revoked */
+
 #ifndef VM_STACK_DEFAULT_FLAGS		/* arch can override this */
 #define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS
 #endif
Index: uml-2.6/mm/memory.c
===================================================================
--- uml-2.6.orig/mm/memory.c	2007-03-08 10:24:24.000000000 +0200
+++ uml-2.6/mm/memory.c	2007-03-08 10:24:25.000000000 +0200
@@ -2504,6 +2504,9 @@
 	if (unlikely(is_vm_hugetlb_page(vma)))
 		return hugetlb_fault(mm, vma, address, write_access);
 
+	if (unlikely(vma->vm_flags & VM_REVOKED))
+		return VM_FAULT_SIGBUS;
+
 	pgd = pgd_offset(mm, address);
 	pud = pud_alloc(mm, pgd, address);
 	if (!pud)
Index: uml-2.6/mm/mmap.c
===================================================================
--- uml-2.6.orig/mm/mmap.c	2007-03-08 10:24:24.000000000 +0200
+++ uml-2.6/mm/mmap.c	2007-03-08 10:24:25.000000000 +0200
@@ -1030,10 +1030,14 @@
 	error = -ENOMEM;
 munmap_back:
 	vma = find_vma_prepare(mm, addr, &prev, &rb_link, &rb_parent);
-	if (vma && vma->vm_start < addr + len) {
-		if (do_munmap(mm, addr, len))
-			return -ENOMEM;
-		goto munmap_back;
+	if (vma) {
+		if (unlikely(vma->vm_flags & VM_REVOKED))
+			return -ENODEV;
+		if (vma->vm_start < addr + len) {
+			if (do_munmap(mm, addr, len))
+				return -ENOMEM;
+			goto munmap_back;
+		}
 	}
 
 	/* Check against address space limit. */
-
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