[patch 10/14] x86, early_ioremap: fix fencepost error

Greg KH
2008-10-16T18:03:48Z

[-- Attachment #1: x86-early_ioremap-fix-fencepost-error.patch --]
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2.6.27-stable review patch. If anyone has any objections, please let us
know.

------------------
From: Alan Cox <alan@redhat.com>

commit c613ec1a7ff3714da11c7c48a13bab03beb5c376 upstream

The x86 implementation of early_ioremap has an off by one error. If we get
an object which ends on the first byte of a page we undermap by one page and
this causes a crash on boot with the ASUS P5QL whose DMI table happens to fit
this alignment.

The size computation is currently

last_addr = phys_addr + size - 1;
npages = (PAGE_ALIGN(last_addr) - phys_addr)

(Consider a request for 1 byte at alignment 0...)

Closes #11693

Debugging work by Ian Campbell/Felix Geyer

Signed-off-by: Alan Cox <alan@rehat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
arch/x86/mm/ioremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -595,7 +595,7 @@ void __init *early_ioremap(unsigned long
*/
offset = phys_addr & ~PAGE_MASK;
phys_addr &= PAGE_MASK;
- size = PAGE_ALIGN(last_addr) - phys_addr;
+ size = PAGE_ALIGN(last_addr + 1) - phys_addr;

/*
* Mappings have to fit in the FIX_BTMAP area.

--