commit 0f0998f6219b25f54f8ab20e3803eff552af3b9c
author Alberto Garcia <berto@igalia.com> Thu Mar 28 18:25:09 2019 +0200
committer Kevin Wolf <kwolf@redhat.com> Tue Apr 02 12:04:44 2019 +0200
tree f19cdec7cdfeb82ff3766d513f11b72cdec673d0
parent 696aaaed579ac5bf5fa336216909b46d3d8f07a8

block: continue until base is found in bdrv_freeze_backing_chain() et al

All three functions that handle the BdrvChild.frozen attribute walk
the backing chain from 'bs' to 'base' and stop either when 'base' is
found or at the end of the chain if 'base' is NULL.

However if 'base' is not found then the functions return without
errors as if it was NULL.

This is wrong: if the caller passed an incorrect parameter that means
that there is a bug in the code.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

diff --git a/block.c b/block.c
index 0a93ee9..3050854 100644
--- a/block.c
+++ b/block.c
@@ -4218,14 +4218,15 @@
 /*
  * Return true if at least one of the backing links between @bs and
  * @base is frozen. @errp is set if that's the case.
+ * @base must be reachable from @bs, or NULL.
  */
 bool bdrv_is_backing_chain_frozen(BlockDriverState *bs, BlockDriverState *base,
                                   Error **errp)
 {
     BlockDriverState *i;
 
-    for (i = bs; i != base && i->backing; i = backing_bs(i)) {
-        if (i->backing->frozen) {
+    for (i = bs; i != base; i = backing_bs(i)) {
+        if (i->backing && i->backing->frozen) {
             error_setg(errp, "Cannot change '%s' link from '%s' to '%s'",
                        i->backing->name, i->node_name,
                        backing_bs(i)->node_name);
@@ -4240,6 +4241,7 @@
  * Freeze all backing links between @bs and @base.
  * If any of the links is already frozen the operation is aborted and
  * none of the links are modified.
+ * @base must be reachable from @bs, or NULL.
  * Returns 0 on success. On failure returns < 0 and sets @errp.
  */
 int bdrv_freeze_backing_chain(BlockDriverState *bs, BlockDriverState *base,
@@ -4251,8 +4253,10 @@
         return -EPERM;
     }
 
-    for (i = bs; i != base && i->backing; i = backing_bs(i)) {
-        i->backing->frozen = true;
+    for (i = bs; i != base; i = backing_bs(i)) {
+        if (i->backing) {
+            i->backing->frozen = true;
+        }
     }
 
     return 0;
@@ -4261,14 +4265,17 @@
 /*
  * Unfreeze all backing links between @bs and @base. The caller must
  * ensure that all links are frozen before using this function.
+ * @base must be reachable from @bs, or NULL.
  */
 void bdrv_unfreeze_backing_chain(BlockDriverState *bs, BlockDriverState *base)
 {
     BlockDriverState *i;
 
-    for (i = bs; i != base && i->backing; i = backing_bs(i)) {
-        assert(i->backing->frozen);
-        i->backing->frozen = false;
+    for (i = bs; i != base; i = backing_bs(i)) {
+        if (i->backing) {
+            assert(i->backing->frozen);
+            i->backing->frozen = false;
+        }
     }
 }