From fbecdf5ed4345a15d1ffc30922d44272a3d60368 Mon Sep 17 00:00:00 2001
Message-Id: <fbecdf5ed4345a15d1ffc30922d44272a3d60368@dist-git>
From: Martin Kletzander <mkletzan@redhat.com>
Date: Fri, 2 Feb 2018 15:21:27 +0100
Subject: [PATCH] util: Clear unused part of the map in virBitmapShrink

Some of the other functions depend on the fact that unused bits and longs are
always zero and it's less error-prone to clear it than fix the other functions.
It's enough to zero out one piece of the map since we're calling realloc() to
get rid of the rest (and updating map_len).

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1540817

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
(cherry picked from commit d6e582da80d07a90f154dc27aca239d44fc2b7b7)
Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
---
 src/conf/domain_conf.c |  4 +++-
 src/util/virbitmap.c   | 30 ++++++++++++++++++++++--------
 src/util/virbitmap.h   |  2 +-
 src/util/virresctrl.c  |  3 ++-
 tests/virbitmaptest.c  |  8 ++++++++
 5 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 181b035647..0af3dd5ab6 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -18365,7 +18365,9 @@ virDomainCachetuneDefParse(virDomainDefPtr def,
 
     /* We need to limit the bitmap to number of vCPUs.  If there's nothing left,
      * then we can just clean up and return 0 immediately */
-    virBitmapShrink(vcpus, def->maxvcpus);
+    if (virBitmapShrink(vcpus, def->maxvcpus) < 0)
+        goto cleanup;
+
     if (virBitmapIsAllClear(vcpus)) {
         ret = 0;
         goto cleanup;
diff --git a/src/util/virbitmap.c b/src/util/virbitmap.c
index b2c5c7a6a5..33cae2f305 100644
--- a/src/util/virbitmap.c
+++ b/src/util/virbitmap.c
@@ -1201,21 +1201,35 @@ virBitmapSubtract(virBitmapPtr a,
 /**
  * virBitmapShrink:
  * @map: Pointer to bitmap
- * @b: last bit position to be excluded from bitmap
+ * @b: Size to reduce the bitmap to
  *
- * Resizes the bitmap so that no more than @b bits will fit into it.  Nothing
- * will change if the size is already smaller than @b.
- *
- * NB: Does not adjust the map->map_len so that a subsequent virBitmapExpand
- * doesn't necessarily need to reallocate.
+ * Reduces the bitmap to size @b.  Nothing will change if the size is already
+ * smaller than or equal to @b.
  */
-void
+int
 virBitmapShrink(virBitmapPtr map,
                 size_t b)
 {
+    size_t nl = 0;
+    size_t nb = 0;
+
     if (!map)
-        return;
+        return 0;
 
     if (map->max_bit >= b)
         map->max_bit = b;
+
+    nl = map->max_bit / VIR_BITMAP_BITS_PER_UNIT;
+    nb = map->max_bit % VIR_BITMAP_BITS_PER_UNIT;
+    map->map[nl] &= ((1UL << nb) - 1);
+
+    nl++;
+    if (nl == map->map_len)
+        return 0;
+
+    if (VIR_REALLOC_N(map->map, nl) < 0)
+        return -1;
+
+    map->map_len = nl;
+    return 0;
 }
diff --git a/src/util/virbitmap.h b/src/util/virbitmap.h
index 2464814055..5a3362a19f 100644
--- a/src/util/virbitmap.h
+++ b/src/util/virbitmap.h
@@ -153,6 +153,6 @@ void virBitmapIntersect(virBitmapPtr a, virBitmapPtr b)
 void virBitmapSubtract(virBitmapPtr a, virBitmapPtr b)
     ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 
-void virBitmapShrink(virBitmapPtr map, size_t b);
+int virBitmapShrink(virBitmapPtr map, size_t b);
 
 #endif
diff --git a/src/util/virresctrl.c b/src/util/virresctrl.c
index 70426199ce..ef388757a7 100644
--- a/src/util/virresctrl.c
+++ b/src/util/virresctrl.c
@@ -941,7 +941,8 @@ virResctrlAllocParseProcessCache(virResctrlInfoPtr resctrl,
     if (!mask)
         return -1;
 
-    virBitmapShrink(mask, resctrl->levels[level]->types[type]->bits);
+    if (virBitmapShrink(mask, resctrl->levels[level]->types[type]->bits) < 0)
+        goto cleanup;
 
     if (virResctrlAllocUpdateMask(alloc, level, type, cache_id, mask) < 0)
         goto cleanup;
diff --git a/tests/virbitmaptest.c b/tests/virbitmaptest.c
index 5bf30b2b1c..a78e4da723 100644
--- a/tests/virbitmaptest.c
+++ b/tests/virbitmaptest.c
@@ -656,6 +656,14 @@ test12(const void *opaque ATTRIBUTE_UNUSED)
 
     TEST_MAP(1024, "34,1023");
 
+    if (virBitmapShrink(map, 35) < 0)
+        goto cleanup;
+    TEST_MAP(35, "34");
+
+    if (virBitmapShrink(map, 34) < 0)
+        goto cleanup;
+    TEST_MAP(34, "");
+
     ret = 0;
 
  cleanup:
-- 
2.16.1