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Subject[PATCH for review] [28/48] i386: fix iounmap's use of vm_struct's size field
Date

From: Jeremy Fitzhardinge <jeremy@goop.org>

get_vm_area always returns an area with an adjacent guard page. That guard
page is included in vm_struct.size. iounmap uses vm_struct.size to
determine how much address space needs to have change_page_attr applied to
it, which will BUG if applied to the guard page.

This patch adds a helper function - get_vm_area_size() in linux/vmalloc.h -
to return the actual size of a vm area, and uses it to make iounmap do the
right thing. There are probably other places which should be using
get_vm_area_size().

Thanks to Dave Young <hidave.darkstar@gmail.com> for debugging the
problem.

[ Andi, it wasn't clear to me whether x86_64 needs the same fix. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Dave Young <hidave.darkstar@gmail.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
arch/i386/mm/ioremap.c | 2 +-
include/linux/vmalloc.h | 7 +++++++
2 files changed, 8 insertions(+), 1 deletion(-)
Index: linux/arch/i386/mm/ioremap.c
===================================================================
--- linux.orig/arch/i386/mm/ioremap.c
+++ linux/arch/i386/mm/ioremap.c
@@ -196,7 +196,7 @@ void iounmap(volatile void __iomem *addr
/* Reset the direct mapping. Can block */
if ((p->flags >> 20) && p->phys_addr < virt_to_phys(high_memory) - 1) {
change_page_attr(virt_to_page(__va(p->phys_addr)),
- p->size >> PAGE_SHIFT,
+ get_vm_area_size(p) >> PAGE_SHIFT,
PAGE_KERNEL);
global_flush_tlb();
}
Index: linux/include/linux/vmalloc.h
===================================================================
--- linux.orig/include/linux/vmalloc.h
+++ linux/include/linux/vmalloc.h
@@ -58,6 +58,13 @@ void vmalloc_sync_all(void);
/*
* Lowlevel-APIs (not for driver use!)
*/
+
+static inline size_t get_vm_area_size(const struct vm_struct *area)
+{
+ /* return actual size without guard page */
+ return area->size - PAGE_SIZE;
+}
+
extern struct vm_struct *get_vm_area(unsigned long size, unsigned long flags);
extern struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
unsigned long start, unsigned long end);
-
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