database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-06-17 17:02:08 +03:00
Code Activity

Process session_preload_libraries within InitPostgres's transaction.

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

12
src/backend/tcop/postgres.c
View File

@ -4076,7 +4076,11 @@ PostgresMain(const char *dbname, const char *username)
* it inside InitPostgres() instead. In particular, anything that
* involves database access should be there, not here.
*/
InitPostgres(dbname, InvalidOid, username, InvalidOid, NULL, false);
InitPostgres(dbname, InvalidOid, /* database to connect to */
username, InvalidOid, /* role to connect as */
!am_walsender, /* honor session_preload_libraries? */
false, /* don't ignore datallowconn */
NULL); /* no out_dbname */
/*
* If the PostmasterContext is still around, recycle the space; we don't
@ -4112,12 +4116,6 @@ PostgresMain(const char *dbname, const char *username)
if (am_walsender)
InitWalSender();
/*
* process any libraries that should be preloaded at backend start (this
* likewise can't be done until GUC settings are complete)
*/
process_session_preload_libraries();
/*
* Send this backend's cancellation info to the frontend.
*/