From: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
This adds special handling for revoked shared memory mappings. We want to
raise SIGBUS if someone accesses a revoked mapping and return ENODEV if
somebody tries to remap one with mmap(2).
Cc: Alan Cox <alan@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
---
include/linux/mm.h | 1 +
mm/memory.c | 3 +++
mm/mmap.c | 12 ++++++++----
3 files changed, 12 insertions(+), 4 deletions(-)
Index: 2.6/include/linux/mm.h
===================================================================
--- 2.6.orig/include/linux/mm.h 2007-12-14 11:33:57.000000000 +0200
+++ 2.6/include/linux/mm.h 2007-12-14 16:40:48.000000000 +0200
@@ -106,6 +106,7 @@ #define VM_INSERTPAGE 0x02000000 /* The
#define VM_ALWAYSDUMP 0x04000000 /* Always include in core dumps */
#define VM_CAN_NONLINEAR 0x08000000 /* Has ->fault & does nonlinear pages */
+#define VM_REVOKED 0x10000000 /* Mapping has been revoked */
#ifndef VM_STACK_DEFAULT_FLAGS /* arch can override this */
#define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS
Index: 2.6/mm/memory.c
===================================================================
--- 2.6.orig/mm/memory.c 2007-11-23 09:58:11.000000000 +0200
+++ 2.6/mm/memory.c 2007-12-14 16:40:49.000000000 +0200
@@ -2530,6 +2530,9 @@ int handle_mm_fault(struct mm_struct *mm
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: 2.6/mm/mmap.c
===================================================================
--- 2.6.orig/mm/mmap.c 2007-12-14 11:33:57.000000000 +0200
+++ 2.6/mm/mmap.c 2007-12-14 16:40:49.000000000 +0200
@@ -1081,10 +1081,14 @@ unsigned long charged = 0;
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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