2008-10-09 16:48:34

by Alan Cox

[permalink] [raw]
Subject: [PATCH] early_ioremap: fix fencepost error

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 <[email protected]>
---

arch/x86/mm/ioremap.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index d4b6e6a..d0975fc 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -595,7 +595,7 @@ void __init *early_ioremap(unsigned long phys_addr, unsigned long size)
*/
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.