[PATCH 2/6] lib/open: fix potential double-free, ensure *database=NULL on error

Subject: [PATCH 2/6] lib/open: fix potential double-free, ensure *database=NULL on error

Date: Sat, 23 Oct 2021 10:22:34 -0300

To: notmuch@notmuchmail.org

Cc: David Bremner

From: David Bremner

During refactoring for 0.32, the code that set notmuch=NULL on various
errors was moved into _finish_open. This meant that the the code which
relied on that to set *database to NULL on error was no longer
correct. It also introduced a potential double free, since the notmuch
struct was deallocated inside _finish_open (via n_d_destroy).

In this commit we revert to "allocator frees", and leave any cleanup
to the caller of _finish_open. This allows us to get back the
behaviour of setting *database to NULL with a small change. Other
callers of _finish_open will need free notmuch on errors.
---
 lib/open.cc            | 13 +++++--------
 test/T590-libconfig.sh |  2 --
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/lib/open.cc b/lib/open.cc
index 8a835e98..77f01f72 100644
--- a/lib/open.cc
+++ b/lib/open.cc
@@ -396,8 +396,6 @@ _finish_open (notmuch_database_t *notmuch,
 				     "       has a newer database format version (%u) than supported by this\n"
 				     "       version of notmuch (%u).\n",
 				     database_path, version, NOTMUCH_DATABASE_VERSION));
-	    notmuch_database_destroy (notmuch);
-	    notmuch = NULL;
 	    status = NOTMUCH_STATUS_FILE_ERROR;
 	    goto DONE;
 	}
@@ -414,8 +412,6 @@ _finish_open (notmuch_database_t *notmuch,
 				     "       requires features (%s)\n"
 				     "       not supported by this version of notmuch.\n",
 				     database_path, incompat_features));
-	    notmuch_database_destroy (notmuch);
-	    notmuch = NULL;
 	    status = NOTMUCH_STATUS_FILE_ERROR;
 	    goto DONE;
 	}
@@ -489,8 +485,6 @@ _finish_open (notmuch_database_t *notmuch,
     } catch (const Xapian::Error &error) {
 	IGNORE_RESULT (asprintf (&message, "A Xapian exception occurred opening database: %s\n",
 				 error.get_msg ().c_str ()));
-	notmuch_database_destroy (notmuch);
-	notmuch = NULL;
 	status = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
     }
   DONE:
@@ -559,10 +553,13 @@ notmuch_database_open_with_config (const char *database_path,
 	    free (message);
     }
 
+    if (status && notmuch) {
+	notmuch_database_destroy (notmuch);
+	notmuch = NULL;
+    }
+
     if (database)
 	*database = notmuch;
-    else
-	talloc_free (notmuch);
 
     if (notmuch)
 	notmuch->open = true;
diff --git a/test/T590-libconfig.sh b/test/T590-libconfig.sh
index ed12b005..a0d70080 100755
--- a/test/T590-libconfig.sh
+++ b/test/T590-libconfig.sh
@@ -862,7 +862,6 @@ cat <<EOF > c_tail3
 EOF
 
 test_begin_subtest "open: database set to null on missing config"
-test_subtest_known_broken
 cat c_head3 - c_tail3 <<'EOF' | test_C ${MAIL_DIR} "/nonexistent"
   notmuch_status_t st = notmuch_database_open_with_config(argv[1],
 							  NOTMUCH_DATABASE_MODE_READ_ONLY,
@@ -876,7 +875,6 @@ EOF
 test_expect_equal_file EXPECTED OUTPUT
 
 test_begin_subtest "open: database set to null on missing config (env)"
-test_subtest_known_broken
 old_NOTMUCH_CONFIG=${NOTMUCH_CONFIG}
 NOTMUCH_CONFIG="/nonexistent"
 cat c_head3 - c_tail3 <<'EOF' | test_C ${MAIL_DIR}
-- 
2.33.0
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