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

commit 77c0c9735bc0ba5898e637a3a20d6bcb50e3f67d upstream.

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 5e90c5d771a7bfaf39e29a5b2aa8ea65fd1169e0..040bbfd1fff6b021d4b9409d540e21a4b8928d9b 100644 (file)
--- a/drivers/hv/hv_balloon.c
+++ b/drivers/hv/hv_balloon.c
@@ -673,7 +673,7 @@ 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
@@ -728,7 +728,7 @@ 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;