Commit-ID: bdc6340f4eb68295b1e7c0ade2356b56dca93d93
Gitweb: http://git.kernel.org/tip/bdc6340f4eb68295b1e7c0ade2356b56dca93d93
Author: Pallipadi, Venkatesh <venkatesh.pallipadi@xxxxxxxxx>
AuthorDate: Thu, 30 Jul 2009 14:43:19 -0700
Committer: H. Peter Anvin <hpa@xxxxxxxxx>
CommitDate: Thu, 30 Jul 2009 17:48:34 -0700
x86, pat: Fix set_memory_wc related corruption
Changeset 3869c4aa18835c8c61b44bd0f3ace36e9d3b5bd0
that went in after 2.6.30-rc1 was a seemingly small change to _set_memory_wc()
to make it complaint with SDM requirements. But, introduced a nasty bug, which
can result in crash and/or strange corruptions when set_memory_wc is used.
One such crash reported here
http://lkml.org/lkml/2009/7/30/94
Actually, that changeset introduced two bugs.
* change_page_attr_set() takes &addr as first argument and can the addr value
might have changed on return, even for single page change_page_attr_set()
call. That will make the second change_page_attr_set() in this routine
operate on unrelated addr, that can eventually cause strange corruptions
and bad page state crash.
* The second change_page_attr_set() call, before setting _PAGE_CACHE_WC, should
clear the earlier _PAGE_CACHE_UC_MINUS, as otherwise cache attribute will not
be WC (will be UC instead).
The patch below fixes both these problems. Sending a single patch to fix both
the problems, as the change is to the same line of code. The change to have a
addr_copy is not very clean. But, it is simpler than making more changes
through various routines in pageattr.c.
A huge thanks to Jerome for reporting this problem and providing a simple test
case that helped us root cause the problem.
Reported-by: Jerome Glisse <glisse@xxxxxxxxxxxxxxx>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>
Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
LKML-Reference: <20090730214319.GA1889@xxxxxxxxxxxxxxxxxxxxx>
Acked-by: Dave Airlie <airlied@xxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx>
---
arch/x86/mm/pageattr.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 1b734d7..895d90e 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -997,12 +997,15 @@ EXPORT_SYMBOL(set_memory_array_uc);
int _set_memory_wc(unsigned long addr, int numpages)
{
int ret;
+ unsigned long addr_copy = addr;
+
ret = change_page_attr_set(&addr, numpages,
__pgprot(_PAGE_CACHE_UC_MINUS), 0);
-
if (!ret) {
- ret = change_page_attr_set(&addr, numpages,
- __pgprot(_PAGE_CACHE_WC), 0);
+ ret = change_page_attr_set_clr(&addr_copy, numpages,
+ __pgprot(_PAGE_CACHE_WC),
+ __pgprot(_PAGE_CACHE_MASK),
+ 0, 0, NULL);
}
return ret;
}
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