Drivers: hv: balloon: don't crash when memory is added in non-sorted order

When we iterate through all HA regions in handle_pg_range() we have an
assumption that all these regions are sorted in the list and the
'start_pfn >= has->end_pfn' check is enough to find the proper region.
Unfortunately it's not the case with WS2016 where host can hot-add regions
in a different order. We end up modifying the wrong HA region and crashing
later on pages online. Modify the check to make sure we found the region
we were searching for while iterating. Fix the same check in pfn_covered()
as well.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c
index b853b4b083bde2c402ee4dbacdd25736b4273e58..43af91362be584b12af80ff27083a8e863f5a10e 100644 (file)
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -714,7 +714,7 @@ static bool pfn_covered(unsigned long start_pfn, unsigned long pfn_cnt)
                 * If the pfn range we are dealing with is not in the current
                 * "hot add block", move on.
                 */
-               if ((start_pfn >= has->end_pfn))
+               if (start_pfn < has->start_pfn || start_pfn >= has->end_pfn)
                        continue;
                /*
                 * If the current hot add-request extends beyond
@@ -768,7 +768,7 @@ static unsigned long handle_pg_range(unsigned long pg_start,
                 * If the pfn range we are dealing with is not in the current
                 * "hot add block", move on.
                 */
-               if ((start_pfn >= has->end_pfn))
+               if (start_pfn < has->start_pfn || start_pfn >= has->end_pfn)
                        continue;
 
                old_covered_state = has->covered_end_pfn;