--- /dev/null
+From f982f91516fa4cfd9d20518833cd04ad714585be Mon Sep 17 00:00:00 2001
+From: Clemens Ladisch <clemens@ladisch.de>
+Date: Tue, 21 Jun 2011 22:09:50 +0200
+Subject: mm: fix wrong vmap address calculations with odd NR_CPUS values
+
+From: Clemens Ladisch <clemens@ladisch.de>
+
+commit f982f91516fa4cfd9d20518833cd04ad714585be upstream.
+
+Commit db64fe02258f ("mm: rewrite vmap layer") introduced code that does
+address calculations under the assumption that VMAP_BLOCK_SIZE is a
+power of two. However, this might not be true if CONFIG_NR_CPUS is not
+set to a power of two.
+
+Wrong vmap_block index/offset values could lead to memory corruption.
+However, this has never been observed in practice (or never been
+diagnosed correctly); what caught this was the BUG_ON in vb_alloc() that
+checks for inconsistent vmap_block indices.
+
+To fix this, ensure that VMAP_BLOCK_SIZE always is a power of two.
+
+BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=31572
+Reported-by: Pavel Kysilka <goldenfish@linuxsoft.cz>
+Reported-by: Matias A. Fonzo <selk@dragora.org>
+Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
+Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
+Cc: Nick Piggin <npiggin@suse.de>
+Cc: Jeremy Fitzhardinge <jeremy@goop.org>
+Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
+Cc: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
+
+---
+ mm/vmalloc.c | 7 ++++---
+ 1 file changed, 4 insertions(+), 3 deletions(-)
+
+--- a/mm/vmalloc.c
++++ b/mm/vmalloc.c
+@@ -732,9 +732,10 @@ static void free_unmap_vmap_area_addr(un
+ #define VMAP_BBMAP_BITS_MIN (VMAP_MAX_ALLOC*2)
+ #define VMAP_MIN(x, y) ((x) < (y) ? (x) : (y)) /* can't use min() */
+ #define VMAP_MAX(x, y) ((x) > (y) ? (x) : (y)) /* can't use max() */
+-#define VMAP_BBMAP_BITS VMAP_MIN(VMAP_BBMAP_BITS_MAX, \
+- VMAP_MAX(VMAP_BBMAP_BITS_MIN, \
+- VMALLOC_PAGES / NR_CPUS / 16))
++#define VMAP_BBMAP_BITS \
++ VMAP_MIN(VMAP_BBMAP_BITS_MAX, \
++ VMAP_MAX(VMAP_BBMAP_BITS_MIN, \
++ VMALLOC_PAGES / roundup_pow_of_two(NR_CPUS) / 16))
+
+ #define VMAP_BLOCK_SIZE (VMAP_BBMAP_BITS * PAGE_SIZE)
+