From: Simon Riggs <simon@2ndQuadrant.com>
Date: Fri, 9 Sep 2016 12:11:25 +0000 (+0100)
Subject: Fix corruption of 2PC recovery with subxacts
X-Git-Tag: REL9_6_0~35
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=1fef3d576e3a8ac69f90faf192997858f1d82f64;p=postgresql

Fix corruption of 2PC recovery with subxacts

Reading 2PC state files during recovery was borked, causing corruptions during
recovery. Effect limited to servers with 2PC, subtransactions and
recovery/replication.

Stas Kelvich, reviewed by Michael Paquier and Pavan Deolasee
---

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 1323fb508d..5415604993 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -1758,8 +1758,9 @@ PrescanPreparedTransactions(TransactionId **xids_p, int *nxids_p)
 			 * need to hold a lock while examining it.  We still acquire the
 			 * lock to modify it, though.
 			 */
-			subxids = (TransactionId *)
-				(buf + MAXALIGN(sizeof(TwoPhaseFileHeader)));
+			subxids = (TransactionId *) (buf +
+								MAXALIGN(sizeof(TwoPhaseFileHeader)) +
+								MAXALIGN(hdr->gidlen));
 			for (i = 0; i < hdr->nsubxacts; i++)
 			{
 				TransactionId subxid = subxids[i];
@@ -1877,8 +1878,9 @@ StandbyRecoverPreparedTransactions(bool overwriteOK)
 			 * Examine subtransaction XIDs ... they should all follow main
 			 * XID.
 			 */
-			subxids = (TransactionId *)
-				(buf + MAXALIGN(sizeof(TwoPhaseFileHeader)));
+			subxids = (TransactionId *) (buf +
+								MAXALIGN(sizeof(TwoPhaseFileHeader)) +
+								MAXALIGN(hdr->gidlen));
 			for (i = 0; i < hdr->nsubxacts; i++)
 			{
 				TransactionId subxid = subxids[i];