From 66c036b4f143d129ea3c2e390ff4e3b449a83ed6 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Tue, 27 Oct 2020 15:37:13 -0400 Subject: [PATCH] Fix use-after-free bug with event triggers and ALTER TABLE. EventTriggerAlterTableEnd neglected to make sure that it built its output list in the right context. In simple cases this was masked because the function is called in PortalContext which will be sufficiently long-lived anyway; but that doesn't make it not a bug. Commit ced138e8c fixed this in HEAD and v13, but mistakenly chose not to back-patch further. Back-patch the same code change all the way (I didn't bother with the test case though, as it would prove nothing in pre-v13 branches). Per report from Arseny Sher. Original fix by Jehan-Guillaume de Rorthais. Discussion: https://postgr.es/m/877drcyprb.fsf@ars-thinkpad Discussion: https://postgr.es/m/20200902193715.6e0269d4@firost --- src/backend/commands/event_trigger.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/backend/commands/event_trigger.c b/src/backend/commands/event_trigger.c index 9a702e4097..b02b35868f 100644 --- a/src/backend/commands/event_trigger.c +++ b/src/backend/commands/event_trigger.c @@ -1799,9 +1799,15 @@ EventTriggerAlterTableEnd(void) /* If no subcommands, don't collect */ if (list_length(currentEventTriggerState->currentCommand->d.alterTable.subcmds) != 0) { + MemoryContext oldcxt; + + oldcxt = MemoryContextSwitchTo(currentEventTriggerState->cxt); + currentEventTriggerState->commandList = lappend(currentEventTriggerState->commandList, currentEventTriggerState->currentCommand); + + MemoryContextSwitchTo(oldcxt); } else pfree(currentEventTriggerState->currentCommand);