E.20. Release 7.4.8

E.20.1. Migration to version 7.4.8

A dump/restore is not required for those running 7.4.X. However, it is one possible way of handling two significant security problems that have been found in the initial contents of 7.4.X system catalogs. A dump/initdb/reload sequence using 7.4.8's initdb will automatically correct these problems.

The larger security problem is that the built-in character set encoding conversion functions can be invoked from SQL commands by unprivileged users, but the functions were not designed for such use and are not secure against malicious choices of arguments. The fix involves changing the declared parameter list of these functions so that they can no longer be invoked from SQL commands. (This does not affect their normal use by the encoding conversion machinery.)

The lesser problem is that the contrib/tsearch2 module creates several functions that are misdeclared to return internal when they do not accept internal arguments. This breaks type safety for all functions using internal arguments.

It is strongly recommended that all installations repair these errors, either by initdb or by following the manual repair procedures given below. The errors at least allow unprivileged database users to crash their server process, and may allow unprivileged users to gain the privileges of a database superuser.

If you wish not to do an initdb, perform the following procedures instead. As the database superuser, do:

BEGIN;
UPDATE pg_proc SET proargtypes[3] = 'internal'::regtype
WHERE pronamespace = 11 AND pronargs = 5
      AND proargtypes[2] = 'cstring'::regtype;
-- The command should report having updated 90 rows;
-- if not, rollback and investigate instead of committing!
COMMIT;

Next, if you have installed contrib/tsearch2, do

BEGIN;
UPDATE pg_proc SET proargtypes[0] = 'internal'::regtype
WHERE oid IN (
    'dex_init(text)'::regprocedure,
    'snb_en_init(text)'::regprocedure,
    'snb_ru_init(text)'::regprocedure,
    'spell_init(text)'::regprocedure,
    'syn_init(text)'::regprocedure
);
-- The command should report having updated 5 rows;
-- if not, rollback and investigate instead of committing!
COMMIT;

If this command fails with a message like "function "dex_init(text)" does not exist", then either tsearch2 is not installed in this database, or you already did the update.

The above procedures must be carried out in each database of an installation, including template1, and ideally including template0 as well. If you do not fix the template databases then any subsequently created databases will contain the same errors. template1 can be fixed in the same way as any other database, but fixing template0 requires additional steps. First, from any database issue

UPDATE pg_database SET datallowconn = true WHERE datname = 'template0';

Next connect to template0 and perform the above repair procedures. Finally, do

-- re-freeze template0:
VACUUM FREEZE;
-- and protect it against future alterations:
UPDATE pg_database SET datallowconn = false WHERE datname = 'template0';

E.20.2. Changes

• Change encoding function signature to prevent misuse

• Change contrib/tsearch2 to avoid unsafe use of INTERNAL function results

• Repair ancient race condition that allowed a transaction to be seen as committed for some purposes (eg SELECT FOR UPDATE) slightly sooner than for other purposes

  This is an extremely serious bug since it could lead to apparent data inconsistencies being briefly visible to applications.

• Repair race condition between relation extension and VACUUM

  This could theoretically have caused loss of a page's worth of freshly-inserted data, although the scenario seems of very low probability. There are no known cases of it having caused more than an Assert failure.

• Fix comparisons of TIME WITH TIME ZONE values

  The comparison code was wrong in the case where the --enable-integer-datetimes configuration switch had been used. NOTE: if you have an index on a TIME WITH TIME ZONE column, it will need to be REINDEXed after installing this update, because the fix corrects the sort order of column values.

• Fix EXTRACT(EPOCH) for TIME WITH TIME ZONE values

• Fix mis-display of negative fractional seconds in INTERVAL values

  This error only occurred when the --enable-integer-datetimes configuration switch had been used.

• Ensure operations done during backend shutdown are counted by statistics collector

  This is expected to resolve reports of pg_autovacuum not vacuuming the system catalogs often enough — it was not being told about catalog deletions caused by temporary table removal during backend exit.

• Additional buffer overrun checks in plpgsql (Neil)

• Fix pg_dump to dump trigger names containing % correctly (Neil)

• Fix contrib/pgcrypto for newer OpenSSL builds (Marko Kreen)

• Still more 64-bit fixes for contrib/intagg

• Prevent incorrect optimization of functions returning RECORD

• Prevent to_char(interval) from dumping core for month-related formats

• Prevent crash on COALESCE(NULL,NULL)

• Fix array_map to call PL functions correctly

• Fix permission checking in ALTER DATABASE RENAME

• Fix ALTER LANGUAGE RENAME

• Make RemoveFromWaitQueue clean up after itself

  This fixes a lock management error that would only be visible if a transaction was kicked out of a wait for a lock (typically by query cancel) and then the holder of the lock released it within a very narrow window.

• Fix problem with untyped parameter appearing in INSERT ... SELECT

• Fix CLUSTER failure after ALTER TABLE SET WITHOUT OIDS