Gitweb: http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a880e7...
Commit: a880e7623397bcb44877b012cd65baa11ad1bbf8
Parent: 6ddc9d3200c25edddd7051f208dbbdd8e16f0734
Author: Roland Dreier <rdreier@cisco.com>
AuthorDate: Mon Sep 15 10:43:35 2008 +0000
Committer: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CommitDate: Tue Oct 7 14:26:18 2008 +1100
powerpc: Avoid integer overflow in page_is_ram()
Commit 8b150478 ("ppc: make phys_mem_access_prot() work with pfns
instead of addresses") fixed page_is_ram() in arch/ppc to avoid overflow
for addresses above 4G on 32-bit kernels. However arch/powerpc's
page_is_ram() is missing the same fix -- it computes a physical address
by doing pfn << PAGE_SHIFT, which overflows if pfn corresponds to a page
above 4G.
In particular this causes pages above 4G to be mapped with the wrong
caching attribute; for example many ppc440-based SoCs have PCI space
above 4G, and mmap()ing MMIO space may end up with a mapping that has
caching enabled.
Fix this by working with the pfn and avoiding the conversion to
physical address that causes the overflow. This patch compares the
pfn to max_pfn, which is a semantic change from the old code -- that
code compared the physical address to high_memory, which corresponds
to max_low_pfn. However, I think that was is another bug, since
highmem pages are still RAM.
Reported-by: vb <vb@vsbe.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---
arch/powerpc/mm/mem.c | 5 ++---
1 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index 1c93c25..98d7bf9 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -75,11 +75,10 @@ static inline pte_t *virt_to_kpte(unsigned long vaddr)
int page_is_ram(unsigned long pfn)
{
- unsigned long paddr = (pfn << PAGE_SHIFT);
-
#ifndef CONFIG_PPC64 /* XXX for now */
- return paddr < __pa(high_memory);
+ return pfn < max_pfn;
#else
+ unsigned long paddr = (pfn << PAGE_SHIFT);
int i;
for (i=0; i < lmb.memory.cnt; i++) {
unsigned long base;
--
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