Commit 9585116b authored Jul 21, 2007 by Jeremy Fitzhardinge Committed by Linus Torvalds Jul 21, 2007

i386: fix iounmap's use of vm_struct's size field



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>
Cc: Dave Young <hidave.darkstar@gmail.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent a2900975

arch/i386/mm/ioremap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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();
		}

include/linux/vmalloc.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -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);