Fix error handling in libpqrcv_connect()

When libpqrcv_connect (also known as walrcv_connect()) failed, it leaked the
libpq connection. In most paths that's fairly harmless, as the calling process
will exit soon after. But e.g. CREATE SUBSCRIPTION could lead to a somewhat
longer lived leak.

Fix by releasing resources, including the libpq connection, on error.

Add a test exercising the error code path. To make it reliable and safe, the
test tries to connect to port=-1, which happens to fail during connection
establishment, rather than during connection string parsing.

Reviewed-by: Noah Misch 
Discussion: https://postgr.es/m/20230121011237[email protected]
Backpatch: 11-

diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index 6eaa84a0315a20801466917d05b005beb1bb7925..78a714fe1b3c22829ab36220a08df18e24c4b713 100644 (file)
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -164,10 +164,7 @@ libpqrcv_connect(const char *conninfo, bool logical, const char *appname,
    conn->streamConn = PQconnectStartParams(keys, vals,
                                             /* expand_dbname = */ true);
    if (PQstatus(conn->streamConn) == CONNECTION_BAD)
-   {
-       *err = pchomp(PQerrorMessage(conn->streamConn));
-       return NULL;
-   }
+       goto bad_connection_errmsg;
 
    /*
     * Poll connection until we have OK or FAILED status.
@@ -209,10 +206,7 @@ libpqrcv_connect(const char *conninfo, bool logical, const char *appname,
    } while (status != PGRES_POLLING_OK && status != PGRES_POLLING_FAILED);
 
    if (PQstatus(conn->streamConn) != CONNECTION_OK)
-   {
-       *err = pchomp(PQerrorMessage(conn->streamConn));
-       return NULL;
-   }
+       goto bad_connection_errmsg;
 
    if (logical)
    {
@@ -223,9 +217,9 @@ libpqrcv_connect(const char *conninfo, bool logical, const char *appname,
        if (PQresultStatus(res) != PGRES_TUPLES_OK)
        {
            PQclear(res);
-           ereport(ERROR,
-                   (errmsg("could not clear search path: %s",
-                           pchomp(PQerrorMessage(conn->streamConn)))));
+           *err = psprintf(_("could not clear search path: %s"),
+                           pchomp(PQerrorMessage(conn->streamConn)));
+           goto bad_connection;
        }
        PQclear(res);
    }
@@ -233,6 +227,16 @@ libpqrcv_connect(const char *conninfo, bool logical, const char *appname,
    conn->logical = logical;
 
    return conn;
+
+   /* error path, using libpq's error message */
+bad_connection_errmsg:
+   *err = pchomp(PQerrorMessage(conn->streamConn));
+
+   /* error path, error already set */
+bad_connection:
+   PQfinish(conn->streamConn);
+   pfree(conn);
+   return NULL;
 }
 
 /*

diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index 590d7f16dac423ddd39e5981664e1d567b246829..85bd97ed8dd207999b584b1c814040be8c4054f5 100644 (file)
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -71,7 +71,15 @@ ERROR:  cannot enable subscription that does not have a slot name
 ALTER SUBSCRIPTION regress_testsub3 REFRESH PUBLICATION;
 ERROR:  ALTER SUBSCRIPTION ... REFRESH is not allowed for disabled subscriptions
 DROP SUBSCRIPTION regress_testsub3;
--- fail - invalid connection string
+-- fail, connection string does not parse
+CREATE SUBSCRIPTION regress_testsub5 CONNECTION 'i_dont_exist=param' PUBLICATION testpub;
+ERROR:  invalid connection string syntax: invalid connection option "i_dont_exist"
+
+-- fail, connection string parses, but doesn't work (and does so without
+-- connecting, so this is reliable and safe)
+CREATE SUBSCRIPTION regress_testsub5 CONNECTION 'port=-1' PUBLICATION testpub;
+ERROR:  could not connect to the publisher: invalid port number: "-1"
+-- fail - invalid connection string during ALTER
 ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 ERROR:  invalid connection string syntax: missing "=" after "foobar" in connection info string
 

diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 855a341a3d90385420b3a8ee3fee4d6b93e0a556..c8a2d08e721df905dfd37579f97cf7f8ffe4d33c 100644 (file)
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -56,7 +56,14 @@ ALTER SUBSCRIPTION regress_testsub3 REFRESH PUBLICATION;
 
 DROP SUBSCRIPTION regress_testsub3;
 
--- fail - invalid connection string
+-- fail, connection string does not parse
+CREATE SUBSCRIPTION regress_testsub5 CONNECTION 'i_dont_exist=param' PUBLICATION testpub;
+
+-- fail, connection string parses, but doesn't work (and does so without
+-- connecting, so this is reliable and safe)
+CREATE SUBSCRIPTION regress_testsub5 CONNECTION 'port=-1' PUBLICATION testpub;
+
+-- fail - invalid connection string during ALTER
 ALTER SUBSCRIPTION regress_testsub CONNECTION 'foobar';
 
 \dRs+