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authorPallipadi, Venkatesh <venkatesh.pallipadi@intel.com>2009-07-30 17:43:19 -0400
committerH. Peter Anvin <hpa@zytor.com>2009-07-30 20:48:34 -0400
commitbdc6340f4eb68295b1e7c0ade2356b56dca93d93 (patch)
tree5ea11ad6a56840ea7c35bafd9c2ca3c6430a3154 /arch/x86/mm/pageattr.c
parent0e83815be719d3391bf5ea24b7fe696c07dbd417 (diff)
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@freedesktop.org> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> LKML-Reference: <20090730214319.GA1889@linux-os.sc.intel.com> Acked-by: Dave Airlie <airlied@redhat.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/mm/pageattr.c')
-rw-r--r--arch/x86/mm/pageattr.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 1b734d7a8966..895d90e1a81b 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -997,12 +997,15 @@ EXPORT_SYMBOL(set_memory_array_uc);
997int _set_memory_wc(unsigned long addr, int numpages) 997int _set_memory_wc(unsigned long addr, int numpages)
998{ 998{
999 int ret; 999 int ret;
1000 unsigned long addr_copy = addr;
1001
1000 ret = change_page_attr_set(&addr, numpages, 1002 ret = change_page_attr_set(&addr, numpages,
1001 __pgprot(_PAGE_CACHE_UC_MINUS), 0); 1003 __pgprot(_PAGE_CACHE_UC_MINUS), 0);
1002
1003 if (!ret) { 1004 if (!ret) {
1004 ret = change_page_attr_set(&addr, numpages, 1005 ret = change_page_attr_set_clr(&addr_copy, numpages,
1005 __pgprot(_PAGE_CACHE_WC), 0); 1006 __pgprot(_PAGE_CACHE_WC),
1007 __pgprot(_PAGE_CACHE_MASK),
1008 0, 0, NULL);
1006 } 1009 }
1007 return ret; 1010 return ret;
1008} 1011}