Fix crash in psql when attempting to reuse old connection

michaelpq · michaelpq · commit f79bea4b6bcd · 2020-04-01T14:45:57.000+09:00
In a psql session, if the connection to the server is abruptly cut, the referenced connection would become NULL as of CheckConnection(). This could cause a hard crash with psql if attempting to connect by reusing the past connection's data because of a null-pointer dereference with either PQhost() or PQdb(). This issue is fixed by making sure that no reuse of the past connection is done if it does not exist. Issue has been introduced by 6e5f8d4, so backpatch down to 12. Reported-by: Hugh Wang Author: Michael Paquier Reviewed-by: Álvaro Herrera, Tom Lane Discussion: https://postgr.es/m/16330-b34835d83619e25d@postgresql.org Backpatch-through: 12
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
@@ -2941,6 +2941,11 @@ do_connect(enum trivalue reuse_previous_specification,
 			reuse_previous = !has_connection_string;
 			break;
 	}
+
+	/* If the old connection does not exist, there is nothing to reuse. */
+	if (!o_conn)
+		reuse_previous = false;
+
 	/* Silently ignore arguments subsequent to a connection string. */
 	if (has_connection_string)
 	{

Original file line number	Diff line number	Diff line change
`@@ -2941,6 +2941,11 @@ do_connect(enum trivalue reuse_previous_specification,`
`2941`	`2941`	`reuse_previous = !has_connection_string;`
`2942`	`2942`	`break;`
`2943`	`2943`	`}`
	`2944`	`+`
	`2945`	`+ /* If the old connection does not exist, there is nothing to reuse. */`
	`2946`	`+ if (!o_conn)`
	`2947`	`+ reuse_previous = false;`
	`2948`	`+`
`2944`	`2949`	`/* Silently ignore arguments subsequent to a connection string. */`
`2945`	`2950`	`if (has_connection_string)`
`2946`	`2951`	`{`