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>Appendix E. Release Notes</TD
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><H1
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><A
NAME="RELEASE-9-6-20"
>E.3. Release 9.6.20</A
></H1
><DIV
CLASS="FORMALPARA"
><P
><B
>Release date: </B
>2020-11-12</P
></DIV
><P
> This release contains a variety of fixes from 9.6.19.
For information about new features in the 9.6 major release, see
<A
HREF="release-9-6.html"
>Section E.23</A
>.
</P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN132010"
>E.3.1. Migration to Version 9.6.20</A
></H2
><P
> A dump/restore is not required for those running 9.6.X.
</P
><P
> However, if you are upgrading from a version earlier than 9.6.16,
see <A
HREF="release-9-6-16.html"
>Section E.7</A
>.
</P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN132015"
>E.3.2. Changes</A
></H2
><P
></P
><UL
><LI
><P
> Block <TT
CLASS="COMMAND"
>DECLARE CURSOR ... WITH HOLD</TT
> and firing of
deferred triggers within index expressions and materialized view
queries (Noah Misch)
</P
><P
> This is essentially a leak in the <SPAN
CLASS="QUOTE"
>"security restricted
operation"</SPAN
> sandbox mechanism. An attacker having permission
to create non-temporary SQL objects could parlay this leak to
execute arbitrary SQL code as a superuser.
</P
><P
> The <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> Project thanks
Etienne Stalmans for reporting this problem.
(CVE-2020-25695)
</P
></LI
><LI
><P
> Fix usage of complex connection-string parameters
in <SPAN
CLASS="APPLICATION"
>pg_dump</SPAN
>,
<SPAN
CLASS="APPLICATION"
>pg_restore</SPAN
>,
<SPAN
CLASS="APPLICATION"
>clusterdb</SPAN
>,
<SPAN
CLASS="APPLICATION"
>reindexdb</SPAN
>,
and <SPAN
CLASS="APPLICATION"
>vacuumdb</SPAN
> (Tom Lane)
</P
><P
> The <TT
CLASS="OPTION"
>-d</TT
> parameter
of <SPAN
CLASS="APPLICATION"
>pg_dump</SPAN
>
and <SPAN
CLASS="APPLICATION"
>pg_restore</SPAN
>, or
the <TT
CLASS="OPTION"
>--maintenance-db</TT
> parameter of the other
programs mentioned, can be a <SPAN
CLASS="QUOTE"
>"connection string"</SPAN
>
containing multiple connection parameters rather than just a
database name. In cases where these programs need to initiate
additional connections, such as parallel processing or processing of
multiple databases, the connection string was forgotten and just the
basic connection parameters (database name, host, port, and
username) were used for the additional connections. This could lead
to connection failures if the connection string included any other
essential information, such as non-default SSL or GSS parameters.
Worse, the connection might succeed but not be encrypted as
intended, or be vulnerable to man-in-the-middle attacks that the
intended connection parameters would have prevented.
(CVE-2020-25694)
</P
></LI
><LI
><P
> When <SPAN
CLASS="APPLICATION"
>psql</SPAN
>'s <TT
CLASS="COMMAND"
>\connect</TT
>
command re-uses connection parameters, ensure that all
non-overridden parameters from a previous connection string are
re-used (Tom Lane)
</P
><P
> This avoids cases where reconnection might fail due to omission of
relevant parameters, such as non-default SSL or GSS options.
Worse, the reconnection might succeed but not be encrypted as
intended, or be vulnerable to man-in-the-middle attacks that the
intended connection parameters would have prevented.
This is largely the same problem as just cited
for <SPAN
CLASS="APPLICATION"
>pg_dump</SPAN
> et al,
although <SPAN
CLASS="APPLICATION"
>psql</SPAN
>'s behavior is more complex
since the user may intentionally override some connection
parameters.
(CVE-2020-25694)
</P
></LI
><LI
><P
> Prevent <SPAN
CLASS="APPLICATION"
>psql</SPAN
>'s <TT
CLASS="COMMAND"
>\gset</TT
>
command from modifying specially-treated variables (Noah Misch)
</P
><P
> <TT
CLASS="COMMAND"
>\gset</TT
> without a prefix would overwrite whatever
variables the server told it to. Thus, a compromised server could
set specially-treated variables such as <TT
CLASS="VARNAME"
>PROMPT1</TT
>,
giving the ability to execute arbitrary shell code in the user's
session.
</P
><P
> The <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> Project thanks
Nick Cleaton for reporting this problem.
(CVE-2020-25696)
</P
></LI
><LI
><P
> Prevent possible data loss from concurrent truncations of SLRU logs
(Noah Misch)
</P
><P
> This rare problem would manifest in later <SPAN
CLASS="QUOTE"
>"apparent
wraparound"</SPAN
> or <SPAN
CLASS="QUOTE"
>"could not access status of
transaction"</SPAN
> errors.
</P
></LI
><LI
><P
> Ensure that SLRU directories are properly fsync'd during checkpoints
(Thomas Munro)
</P
><P
> This prevents possible data loss in a subsequent operating system
crash.
</P
></LI
><LI
><P
> Fix <TT
CLASS="COMMAND"
>ALTER ROLE</TT
> for users with
the <TT
CLASS="LITERAL"
>BYPASSRLS</TT
> attribute (Tom Lane, Stephen Frost)
</P
><P
> The <TT
CLASS="LITERAL"
>BYPASSRLS</TT
> attribute is only allowed to be
changed by superusers, but other <TT
CLASS="COMMAND"
>ALTER ROLE</TT
>
operations, such as password changes, should be allowed with only
ordinary permission checks. The previous coding erroneously
restricted all changes on such a role to superusers.
</P
></LI
><LI
><P
> Fix handling of expressions in <TT
CLASS="COMMAND"
>CREATE TABLE LIKE</TT
>
with inheritance (Tom Lane)
</P
><P
> If a <TT
CLASS="COMMAND"
>CREATE TABLE</TT
> command uses
both <TT
CLASS="LITERAL"
>LIKE</TT
> and traditional inheritance, column
references in <TT
CLASS="LITERAL"
>CHECK</TT
> constraints and expression
indexes that came from a <TT
CLASS="LITERAL"
>LIKE</TT
> parent table tended
to get mis-numbered, resulting in wrong answers and/or bizarre error
messages. The same could happen in <TT
CLASS="LITERAL"
>GENERATED</TT
>
expressions, in branches that have that feature.
</P
></LI
><LI
><P
> Fix off-by-one conversion of negative years to BC dates
in <CODE
CLASS="FUNCTION"
>to_date()</CODE
>
and <CODE
CLASS="FUNCTION"
>to_timestamp()</CODE
> (Dar Alathar-Yemen, Tom Lane)
</P
><P
> Also, arrange for the combination of a negative year and an
explicit <SPAN
CLASS="QUOTE"
>"BC"</SPAN
> marker to cancel out and produce AD.
</P
></LI
><LI
><P
> Ensure that standby servers will archive WAL timeline history files
when <TT
CLASS="VARNAME"
>archive_mode</TT
> is set
to <TT
CLASS="LITERAL"
>always</TT
> (Grigory Smolkin, Fujii Masao)
</P
><P
> This oversight could lead to failure of subsequent PITR recovery
attempts.
</P
></LI
><LI
><P
> During <SPAN
CLASS="QUOTE"
>"smart"</SPAN
> shutdown, don't terminate background
processes until all client (foreground) sessions are done (Tom Lane)
</P
><P
> The previous behavior broke parallel query processing, since the
postmaster would terminate parallel workers and refuse to launch any
new ones. It also caused autovacuum to cease functioning, which
could have dire long-term effects if the surviving client sessions
make a lot of data changes.
</P
></LI
><LI
><P
> Avoid recursive consumption of stack space while processing signals
in the postmaster (Tom Lane)
</P
><P
> Heavy use of parallel processing has been observed to cause
postmaster crashes due to too many concurrent signals requesting
creation of a parallel worker process.
</P
></LI
><LI
><P
> Avoid running <SPAN
CLASS="SYSTEMITEM"
>atexit</SPAN
> handlers when exiting
due to SIGQUIT (Kyotaro Horiguchi, Tom Lane)
</P
><P
> Most server processes followed this practice already, but the
archiver process was overlooked. Backends that were still waiting
for a client startup packet got it wrong, too.
</P
></LI
><LI
><P
> Avoid misoptimization of subquery qualifications that reference
apparently-constant grouping columns (Tom Lane)
</P
><P
> A <SPAN
CLASS="QUOTE"
>"constant"</SPAN
> subquery output column isn't really
constant if it is a grouping column that appears in only some of the
grouping sets.
</P
></LI
><LI
><P
> Avoid failure when SQL function inlining changes the shape of a
potentially-hashable subplan comparison expression (Tom Lane)
</P
></LI
><LI
><P
> While building or re-building an index, tolerate the appearance of
new HOT chains due to concurrent updates
(Anastasia Lubennikova, Álvaro Herrera)
</P
><P
> This oversight could lead to <SPAN
CLASS="QUOTE"
>"failed to find parent tuple for
heap-only tuple"</SPAN
> errors.
</P
></LI
><LI
><P
> Ensure that data is detoasted before being inserted into a BRIN
index (Tomas Vondra)
</P
><P
> Index entries are not supposed to contain out-of-line TOAST
pointers, but BRIN didn't get that memo. This could lead to errors
like <SPAN
CLASS="QUOTE"
>"missing chunk number 0 for toast value NNN"</SPAN
>.
(If you are faced with such an error from an existing
index, <TT
CLASS="COMMAND"
>REINDEX</TT
> should be enough to fix it.)
</P
></LI
><LI
><P
> Handle concurrent desummarization correctly during BRIN index scans
(Alexander Lakhin, Álvaro Herrera)
</P
><P
> Previously, if a page range was desummarized at just the wrong time,
an index scan might falsely raise an error indicating index
corruption.
</P
></LI
><LI
><P
> Fix rare <SPAN
CLASS="QUOTE"
>"lost saved point in index"</SPAN
> errors in scans of
multicolumn GIN indexes (Tom Lane)
</P
></LI
><LI
><P
> Fix use-after-free hazard when an event trigger monitors
an <TT
CLASS="COMMAND"
>ALTER TABLE</TT
> operation (Jehan-Guillaume de
Rorthais)
</P
></LI
><LI
><P
> Fix incorrect error message about inconsistent moving-aggregate
data types (Jeff Janes)
</P
></LI
><LI
><P
> Avoid lockup when a parallel worker reports a very long error
message (Vignesh C)
</P
></LI
><LI
><P
> Avoid unnecessary failure when transferring very large payloads
through shared memory queues (Markus Wanner)
</P
></LI
><LI
><P
> Fix relation cache memory leaks with RLS policies (Tom Lane)
</P
></LI
><LI
><P
> Fix small memory leak when SIGHUP processing decides that a new GUC
variable value cannot be applied without a restart (Tom Lane)
</P
></LI
><LI
><P
> Make <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> support arbitrary-length lines
in <TT
CLASS="FILENAME"
>.pgpass</TT
> files (Tom Lane)
</P
><P
> This is mostly useful to allow using very long security tokens as
passwords.
</P
></LI
><LI
><P
> In <SPAN
CLASS="APPLICATION"
>libpq</SPAN
> for Windows,
call <CODE
CLASS="FUNCTION"
>WSAStartup()</CODE
> once per process
and <CODE
CLASS="FUNCTION"
>WSACleanup()</CODE
> not at all (Tom Lane,
Alexander Lakhin)
</P
><P
> Previously, <SPAN
CLASS="APPLICATION"
>libpq</SPAN
>
invoked <CODE
CLASS="FUNCTION"
>WSAStartup()</CODE
> at connection start
and <CODE
CLASS="FUNCTION"
>WSACleanup()</CODE
> at connection cleanup.
However, it appears that calling <CODE
CLASS="FUNCTION"
>WSACleanup()</CODE
>
can interfere with other program operations; notably, we have
observed rare failures to emit expected output to stdout. There
appear to be no ill effects from omitting the call, so do that.
(This also eliminates a performance issue from repeated DLL loads and
unloads when a program performs a series of database connections.)
</P
></LI
><LI
><P
> Fix <SPAN
CLASS="APPLICATION"
>ecpg</SPAN
> library's per-thread
initialization logic for Windows (Tom Lane, Alexander Lakhin)
</P
><P
> Multi-threaded <SPAN
CLASS="APPLICATION"
>ecpg</SPAN
> applications could
suffer rare misbehavior due to incorrect locking.
</P
></LI
><LI
><P
> On Windows, make <SPAN
CLASS="APPLICATION"
>psql</SPAN
> read the output of
a backtick command in text mode, not binary mode (Tom Lane)
</P
><P
> This ensures proper handling of newlines.
</P
></LI
><LI
><P
> Ensure that <SPAN
CLASS="APPLICATION"
>pg_dump</SPAN
> collects per-column
information about extension configuration tables (Fabrízio de
Royes Mello, Tom Lane)
</P
><P
> Failure to do this led to crashes when
specifying <TT
CLASS="OPTION"
>--inserts</TT
>, or underspecified (though
usually correct) <TT
CLASS="COMMAND"
>COPY</TT
> commands when
using <TT
CLASS="COMMAND"
>COPY</TT
> to reload the tables' data.
</P
></LI
><LI
><P
> Make <SPAN
CLASS="APPLICATION"
>pg_upgrade</SPAN
> check for pre-existence
of tablespace directories in the target cluster (Bruce Momjian)
</P
></LI
><LI
><P
> Fix potential memory leak in <TT
CLASS="FILENAME"
>contrib/pgcrypto</TT
>
(Michael Paquier)
</P
></LI
><LI
><P
> Add check for an unlikely failure case
in <TT
CLASS="FILENAME"
>contrib/pgcrypto</TT
> (Daniel Gustafsson)
</P
></LI
><LI
><P
> Use <TT
CLASS="LITERAL"
>return</TT
> not <TT
CLASS="LITERAL"
>exit()</TT
> in
<SPAN
CLASS="APPLICATION"
>configure</SPAN
>'s
test programs (Peter Eisentraut)
</P
><P
> This avoids failures with pickier compilers.
</P
></LI
><LI
><P
> Update time zone data files to <SPAN
CLASS="APPLICATION"
>tzdata</SPAN
>
release 2020d for DST law changes in Fiji, Morocco, Palestine, the
Canadian Yukon, Macquarie Island, and Casey Station (Antarctica);
plus historical corrections for France, Hungary, Monaco, and
Palestine.
</P
></LI
><LI
><P
> Sync our copy of the timezone library with IANA tzcode release 2020d
(Tom Lane)
</P
><P
> This absorbs upstream's change of <SPAN
CLASS="APPLICATION"
>zic</SPAN
>'s
default output option from <SPAN
CLASS="QUOTE"
>"fat"</SPAN
>
to <SPAN
CLASS="QUOTE"
>"slim"</SPAN
>. That's just cosmetic for our purposes, as
we continue to select the <SPAN
CLASS="QUOTE"
>"fat"</SPAN
> mode in pre-v13
branches. This change also ensures
that <CODE
CLASS="FUNCTION"
>strftime()</CODE
> does not
change <TT
CLASS="VARNAME"
>errno</TT
> unless it fails.
</P
></LI
></UL
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