lib: talloc: Allow destructors to reparent the object they're called on.

If a destructor returns failure (-1) when freeing a child, talloc
must then reparent the child.

Firstly it tries the owner of any reference, next the parent of the
current object calling _talloc_free_children_internal(), and finally
the null context in the last resort.

If a destructor reparented its own object, which can be a very
desirable thing to do (a destructor can make a decision it isn't
time to die yet, and as the parent may be going away it might
want to move itself to longer-term storage) then this new parent
gets overwritten by the existing reparenting logic.

This patch checks when freeing a child if it already reparented
itself, and if it did doesn't then overwrite the new parent.

Makes destructors more flexible.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Ira Cooper <ira@samba.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/talloc/talloc.c b/lib/talloc/talloc.c
index 1ccb039ff7..46f10f4697 100644
--- a/lib/talloc/talloc.c
+++ b/lib/talloc/talloc.c
@@ -1470,6 +1470,13 @@ static inline void _talloc_free_children_internal(struct talloc_chunk *tc,
 			if (p) new_parent = TC_PTR_FROM_CHUNK(p);
 		}
 		if (unlikely(_talloc_free_internal(child, location) == -1)) {
+			if (talloc_parent_chunk(child) != tc) {
+				/*
+				 * Destructor already reparented this child.
+				 * No further reparenting needed.
+				 */
+				return;
+			}
 			if (new_parent == null_context) {
 				struct talloc_chunk *p = talloc_parent_chunk(ptr);
 				if (p) new_parent = TC_PTR_FROM_CHUNK(p);