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Process session_preload_libraries within InitPostgres's transaction.

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Previously we did this after InitPostgres, at a somewhat randomly chosen
place within PostgresMain.  However, since commit a0ffa885e doing this
outside a transaction can cause a crash, if we need to check permissions
while replacing a placeholder GUC.  (Besides which, a preloaded library
could itself want to do database access within _PG_init.)

To avoid needing an additional transaction start/end in every session,
move the process_session_preload_libraries call to within InitPostgres's
transaction.  That requires teaching the code not to call it when
InitPostgres is called from somewhere other than PostgresMain, since
we don't want session_preload_libraries to affect background workers.
The most future-proof solution here seems to be to add an additional
flag parameter to InitPostgres; fortunately, we're not yet very worried
about API stability for v15.

Doing this also exposed the fact that we're currently honoring
session_preload_libraries in walsenders, even those not connected to
any database.  This seems, at minimum, a POLA violation: walsenders
are not interactive sessions.  Let's stop doing that.

(All these comments also apply to local_preload_libraries, of course.)

Per report from Gurjeet Singh (thanks also to Nathan Bossart and Kyotaro
Horiguchi for review).  Backpatch to v15 where a0ffa885e came in.

Discussion: https://postgr.es/m/CABwTF4VEpwTHhRQ+q5MiC5ucngN-whN-PdcKeufX7eLSoAfbZA@mail.gmail.com
This commit is contained in:
Tom Lane
2022-07-25 10:27:43 -04:00
parent 7a08f78aea
commit b35617de37
6 changed files with 64 additions and 25 deletions
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12
src/backend/postmaster/postmaster.c
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@@ -5654,7 +5654,11 @@ BackgroundWorkerInitializeConnection(const char *dbname, const char *username, u
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("database connection requirement not indicated during registration")));
InitPostgres(dbname, InvalidOid, username, InvalidOid, NULL, (flags & BGWORKER_BYPASS_ALLOWCONN) != 0);
InitPostgres(dbname, InvalidOid, /* database to connect to */
username, InvalidOid, /* role to connect as */
false, /* never honor session_preload_libraries */
(flags & BGWORKER_BYPASS_ALLOWCONN) != 0, /* ignore datallowconn? */
NULL); /* no out_dbname */
/* it had better not gotten out of "init" mode yet */
if (!IsInitProcessingMode())
@@ -5677,7 +5681,11 @@ BackgroundWorkerInitializeConnectionByOid(Oid dboid, Oid useroid, uint32 flags)
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("database connection requirement not indicated during registration")));
InitPostgres(NULL, dboid, NULL, useroid, NULL, (flags & BGWORKER_BYPASS_ALLOWCONN) != 0);
InitPostgres(NULL, dboid, /* database to connect to */
NULL, useroid, /* role to connect as */
false, /* never honor session_preload_libraries */
(flags & BGWORKER_BYPASS_ALLOWCONN) != 0, /* ignore datallowconn? */
NULL); /* no out_dbname */
/* it had better not gotten out of "init" mode yet */
if (!IsInitProcessingMode())