Fix guc_malloc calls for consistency and OOM checks

danielgustafsson · danielgustafsson · commit 8afec4ef67a2 · 2025-03-27T22:57:34.000+01:00
check_createrole_self_grant and check_synchronized_standby_slots were allocating memory on a LOG elevel without checking if the allocation succeeded or not, which would have led to a segfault on allocation failure. On top of that, a number of callsites were using the ERROR level, relying on erroring out rather than returning false to allow the GUC machinery handle it gracefully. Other callsites used WARNING instead of LOG. While neither being not wrong, this changes all check_ functions do it consistently with LOG. init_custom_variable gets a promoted elevel to FATAL to keep the guc_malloc error handling in line with the rest of the error handling in that function which already call FATAL. If we encounter an OOM in this callsite there is no graceful handling to be had, better to error out hard. Backpatch the fix to check_createrole_self_grant down to v16 and the fix to check_synchronized_standby_slots down to v17 where they were introduced. Author: Daniel Gustafsson <daniel@yesql.se> Reported-by: Nikita <pm91.arapov@gmail.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Bug: #18845 Discussion: https://postgr.es/m/18845-582c6e10247377ec@postgresql.org Backpatch-through: 16
diff --git a/src/backend/commands/user.c b/src/backend/commands/user.c
@@ -2553,6 +2553,8 @@ check_createrole_self_grant(char **newval, void **extra, GucSource source)
 	list_free(elemlist);
 
 	result = (unsigned *) guc_malloc(LOG, sizeof(unsigned));
+	if (!result)
+		return false;
 	*result = options;
 	*extra = result;
 
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
@@ -2521,6 +2521,8 @@ check_synchronized_standby_slots(char **newval, void **extra, GucSource source)
 
 	/* GUC extra value must be guc_malloc'd, not palloc'd */
 	config = (SyncStandbySlotsConfigData *) guc_malloc(LOG, size);
+	if (!config)
+		return false;
 
 	/* Transform the data into SyncStandbySlotsConfigData */
 	config->nslotnames = list_length(elemlist);
