From 3bdc110e167d7e0f20022dea48ec51b1f46369cb Mon Sep 17 00:00:00 2001
From: Gary Lockyer <gary@catalyst.net.nz>
Date: Wed, 13 May 2020 10:56:56 +1200
Subject: [PATCH 10/11] CVE-2020-10730: lib ldb: Check if
 ldb_lock_backend_callback called twice

Prevent use after free issues if ldb_lock_backend_callback is called
twice, usually due to ldb_module_done being called twice. This can happen if a
module ignores the return value from function a function that calls
ldb_module_done as part of it's error handling.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14364

Signed-off-by: Gary Lockyer <gary@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
---
 lib/ldb/common/ldb.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/ldb/common/ldb.c b/lib/ldb/common/ldb.c
index 44a487ba987..090d41dde69 100644
--- a/lib/ldb/common/ldb.c
+++ b/lib/ldb/common/ldb.c
@@ -1009,6 +1009,13 @@ static int ldb_lock_backend_callback(struct ldb_request *req,
 	struct ldb_db_lock_context *lock_context;
 	int ret;
 
+	if (req->context == NULL) {
+		/*
+		 * The usual way to get here is to ignore the return codes
+		 * and continuing processing after an error.
+		 */
+		abort();
+	}
 	lock_context = talloc_get_type(req->context,
 				       struct ldb_db_lock_context);
 
@@ -1023,7 +1030,7 @@ static int ldb_lock_backend_callback(struct ldb_request *req,
 		 * If this is a LDB_REPLY_DONE or an error, unlock the
 		 * DB by calling the destructor on this context
 		 */
-		talloc_free(lock_context);
+		TALLOC_FREE(req->context);
 		return ret;
 	}
 
-- 
2.17.1