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Subject[PATCH 4.14 31/64] x86/mm: Fix overlap of i386 CPU_ENTRY_AREA with FIX_BTMAP
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: William Grant <william.grant@canonical.com>

commit 55f49fcb879fbeebf2a8c1ac7c9e6d90df55f798

Since commit 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the
fixmap"), i386's CPU_ENTRY_AREA has been mapped to the memory area just
below FIXADDR_START. But already immediately before FIXADDR_START is the
FIX_BTMAP area, which means that early_ioremap can collide with the entry
area.

It's especially bad on PAE where FIX_BTMAP_BEGIN gets aligned to exactly
match CPU_ENTRY_AREA_BASE, so the first early_ioremap slot clobbers the
IDT and causes interrupts during early boot to reset the system.

The overlap wasn't a problem before the CPU entry area was introduced,
as the fixmap has classically been preceded by the pkmap or vmalloc
areas, neither of which is used until early_ioremap is out of the
picture.

Relocate CPU_ENTRY_AREA to below FIX_BTMAP, not just below the permanent
fixmap area.

Fixes: commit 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap")
Signed-off-by: William Grant <william.grant@canonical.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/7041d181-a019-e8b9-4e4e-48215f841e2c@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
arch/x86/include/asm/fixmap.h | 6 ++++--
arch/x86/include/asm/pgtable_32_types.h | 5 +++--
2 files changed, 7 insertions(+), 4 deletions(-)

--- a/arch/x86/include/asm/fixmap.h
+++ b/arch/x86/include/asm/fixmap.h
@@ -137,8 +137,10 @@ enum fixed_addresses {

extern void reserve_top_address(unsigned long reserve);

-#define FIXADDR_SIZE (__end_of_permanent_fixed_addresses << PAGE_SHIFT)
-#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
+#define FIXADDR_SIZE (__end_of_permanent_fixed_addresses << PAGE_SHIFT)
+#define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
+#define FIXADDR_TOT_SIZE (__end_of_fixed_addresses << PAGE_SHIFT)
+#define FIXADDR_TOT_START (FIXADDR_TOP - FIXADDR_TOT_SIZE)

extern int fixmaps_set;

--- a/arch/x86/include/asm/pgtable_32_types.h
+++ b/arch/x86/include/asm/pgtable_32_types.h
@@ -44,8 +44,9 @@ extern bool __vmalloc_start_set; /* set
*/
#define CPU_ENTRY_AREA_PAGES (NR_CPUS * 40)

-#define CPU_ENTRY_AREA_BASE \
- ((FIXADDR_START - PAGE_SIZE * (CPU_ENTRY_AREA_PAGES + 1)) & PMD_MASK)
+#define CPU_ENTRY_AREA_BASE \
+ ((FIXADDR_TOT_START - PAGE_SIZE * (CPU_ENTRY_AREA_PAGES + 1)) \
+ & PMD_MASK)

#define PKMAP_BASE \
((CPU_ENTRY_AREA_BASE - PAGE_SIZE) & PMD_MASK)

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