talloc: Allow nested pools.

Signed-off-by: Volker Lendecke <vl@samba.org>
Signed-off-by: Jeremy Allison <jra@samba.org>
(cherry picked from commit 20ad6d7aa3dc5e7db4d886202f757ac1f68287d4)

3 files changed, 52 insertions, 24 deletions

diff --git a/lib/talloc/talloc.c b/lib/talloc/talloc.c
index 5d13567e6d8..198bab95f6a 100644
--- a/lib/talloc/talloc.c
+++ b/lib/talloc/talloc.c
@@ -672,13 +672,6 @@ _PUBLIC_ void *talloc_pool(const void *context, size_t size)
 	tc = talloc_chunk_from_ptr(result);
 	pool_hdr = talloc_pool_from_chunk(tc);
 
-	if (unlikely(tc->flags & TALLOC_FLAG_POOLMEM)) {
-		/* We don't handle this correctly, so fail. */
-		talloc_log("talloc: cannot allocate pool off another pool %s\n",
-			   talloc_get_name(context));
-		talloc_free(result);
-		return NULL;
-	}
 	tc->flags |= TALLOC_FLAG_POOL;
 	tc->size = 0;
 
@@ -836,10 +829,19 @@ static inline void _talloc_free_poolmem(struct talloc_chunk *tc,
 		 */
 		pool_tc->name = location;
 
-		talloc_memlimit_update_on_free(pool_tc);
-
-		TC_INVALIDATE_FULL_CHUNK(pool_tc);
-		free(pool);
+		if (pool_tc->flags & TALLOC_FLAG_POOLMEM) {
+			_talloc_free_poolmem(pool_tc, location);
+		} else {
+			/*
+			 * The talloc_memlimit_update_on_free()
+			 * call takes into account the
+			 * prefix TP_HDR_SIZE allocated before
+			 * the pool talloc_chunk.
+			 */
+			talloc_memlimit_update_on_free(pool_tc);
+			TC_INVALIDATE_FULL_CHUNK(pool_tc);
+			free(pool);
+		}
 		return;
 	}
 
@@ -869,6 +871,7 @@ static inline void _talloc_free_children_internal(struct talloc_chunk *tc,
 static inline int _talloc_free_internal(void *ptr, const char *location)
 {
 	struct talloc_chunk *tc;
+	void *ptr_to_free;
 
 	if (unlikely(ptr == NULL)) {
 		return -1;
@@ -961,15 +964,13 @@ static inline int _talloc_free_internal(void *ptr, const char *location)
 		}
 
 		/*
-		 * This call takes into account the
-		 * prefix TP_HDR_SIZE allocated before
-		 * the pool talloc_chunk.
-		 */
-		talloc_memlimit_update_on_free(tc);
-
-		TC_INVALIDATE_FULL_CHUNK(tc);
-		free(pool);
-		return 0;
+		 * With object_count==0, a pool becomes a normal piece of
+		 * memory to free. If it's allocated inside a pool, it needs
+		 * to be freed as poolmem, else it needs to be just freed.
+		*/
+		ptr_to_free = pool;
+	} else {
+		ptr_to_free = tc;
 	}
 
 	if (tc->flags & TALLOC_FLAG_POOLMEM) {
@@ -980,7 +981,7 @@ static inline int _talloc_free_internal(void *ptr, const char *location)
 	talloc_memlimit_update_on_free(tc);
 
 	TC_INVALIDATE_FULL_CHUNK(tc);
-	free(tc);
+	free(ptr_to_free);
 	return 0;
 }
 
@@ -2632,7 +2633,9 @@ static void talloc_memlimit_update_on_free(struct talloc_chunk *tc)
 	/*
 	 * Pool entries don't count. Only the pools
 	 * themselves are counted as part of the memory
-	 * limits.
+	 * limits. Note that this also takes care of
+	 * nested pools which have both flags
+	 * TALLOC_FLAG_POOLMEM|TALLOC_FLAG_POOL set.
 	 */
 	if (tc->flags & TALLOC_FLAG_POOLMEM) {
 		return;
diff --git a/lib/talloc/talloc.h b/lib/talloc/talloc.h
index f3cbcd0e7c0..aa9864b436f 100644
--- a/lib/talloc/talloc.h
+++ b/lib/talloc/talloc.h
@@ -839,8 +839,7 @@ void *talloc_find_parent_bytype(const void *ptr, #type);
  * talloc pool to a talloc parent outside the pool, the whole pool memory is
  * not free(3)'ed until that moved chunk is also talloc_free()ed.
  *
- * @param[in]  context  The talloc context to hang the result off (must not
- *			be another pool).
+ * @param[in]  context  The talloc context to hang the result off.
  *
  * @param[in]  size     Size of the talloc pool.
  *
diff --git a/lib/talloc/testsuite.c b/lib/talloc/testsuite.c
index 426c31a8f24..f04f4f1cc72 100644
--- a/lib/talloc/testsuite.c
+++ b/lib/talloc/testsuite.c
@@ -1267,6 +1267,30 @@ static bool test_pool_steal(void)
 	return true;
 }
 
+static bool test_pool_nest(void)
+{
+	void *p1, *p2, *p3;
+	void *e = talloc_new(NULL);
+
+	p1 = talloc_pool(NULL, 1024);
+	torture_assert("talloc_pool", p1 != NULL, "failed");
+
+	p2 = talloc_pool(p1, 500);
+	torture_assert("talloc_pool", p2 != NULL, "failed");
+
+	p3 = talloc_size(p2, 10);
+
+	talloc_steal(e, p3);
+
+	talloc_free(p2);
+
+	talloc_free(p3);
+
+	talloc_free(p1);
+
+	return true;
+}
+
 static bool test_free_ref_null_context(void)
 {
 	void *p1, *p2, *p3;
@@ -1567,6 +1591,8 @@ bool torture_local_talloc(struct torture_context *tctx)
 	setlinebuf(stdout);
 
 	test_reset();
+	ret &= test_pool_nest();
+	test_reset();
 	ret &= test_ref1();
 	test_reset();
 	ret &= test_ref2();