diff --git a/block.c b/block.c
index 33804cd..a2bffce 100644
--- a/block.c
+++ b/block.c
@@ -2126,6 +2126,8 @@
     BlockDriverState *old_bs = child->bs;
     int i;
 
+    assert(!child->frozen);
+
     if (old_bs && new_bs) {
         assert(bdrv_get_aio_context(old_bs) == bdrv_get_aio_context(new_bs));
     }
@@ -2342,6 +2344,10 @@
     bool update_inherits_from = bdrv_chain_contains(bs, backing_hd) &&
         bdrv_inherits_from_recursive(backing_hd, bs);
 
+    if (bdrv_is_backing_chain_frozen(bs, backing_bs(bs), errp)) {
+        return;
+    }
+
     if (backing_hd) {
         bdrv_ref(backing_hd);
     }
@@ -3721,6 +3727,11 @@
         if (!should_update_child(c, to)) {
             continue;
         }
+        if (c->frozen) {
+            error_setg(errp, "Cannot change '%s' link to '%s'",
+                       c->name, from->node_name);
+            goto out;
+        }
         list = g_slist_prepend(list, c);
         perm |= c->perm;
         shared &= c->shared_perm;
@@ -3933,6 +3944,63 @@
 }
 
 /*
+ * Return true if at least one of the backing links between @bs and
+ * @base is frozen. @errp is set if that's the case.
+ */
+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) {
+            error_setg(errp, "Cannot change '%s' link from '%s' to '%s'",
+                       i->backing->name, i->node_name,
+                       backing_bs(i)->node_name);
+            return true;
+        }
+    }
+
+    return false;
+}
+
+/*
+ * 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.
+ * Returns 0 on success. On failure returns < 0 and sets @errp.
+ */
+int bdrv_freeze_backing_chain(BlockDriverState *bs, BlockDriverState *base,
+                              Error **errp)
+{
+    BlockDriverState *i;
+
+    if (bdrv_is_backing_chain_frozen(bs, base, errp)) {
+        return -EPERM;
+    }
+
+    for (i = bs; i != base && i->backing; i = backing_bs(i)) {
+        i->backing->frozen = true;
+    }
+
+    return 0;
+}
+
+/*
+ * Unfreeze all backing links between @bs and @base. The caller must
+ * ensure that all links are frozen before using this function.
+ */
+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;
+    }
+}
+
+/*
  * Drops images above 'base' up to and including 'top', and sets the image
  * above 'top' to have base as its backing file.
  *
@@ -3981,6 +4049,14 @@
         goto exit;
     }
 
+    /* This function changes all links that point to top and makes
+     * them point to base. Check that none of them is frozen. */
+    QLIST_FOREACH(c, &top->parents, next_parent) {
+        if (c->frozen) {
+            goto exit;
+        }
+    }
+
     /* If 'base' recursively inherits from 'top' then we should set
      * base->inherits_from to top->inherits_from after 'top' and all
      * other intermediate nodes have been dropped.
diff --git a/include/block/block.h b/include/block/block.h
index 6a758a7..b0c04f1 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -353,6 +353,11 @@
 BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
                                     BlockDriverState *bs);
 BlockDriverState *bdrv_find_base(BlockDriverState *bs);
+bool bdrv_is_backing_chain_frozen(BlockDriverState *bs, BlockDriverState *base,
+                                  Error **errp);
+int bdrv_freeze_backing_chain(BlockDriverState *bs, BlockDriverState *base,
+                              Error **errp);
+void bdrv_unfreeze_backing_chain(BlockDriverState *bs, BlockDriverState *base);
 
 
 typedef struct BdrvCheckResult {
diff --git a/include/block/block_int.h b/include/block/block_int.h
index a23caba..438feba 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -711,6 +711,12 @@
     uint64_t backup_perm;
     uint64_t backup_shared_perm;
 
+    /*
+     * This link is frozen: the child can neither be replaced nor
+     * detached from the parent.
+     */
+    bool frozen;
+
     QLIST_ENTRY(BdrvChild) next;
     QLIST_ENTRY(BdrvChild) next_parent;
 };