From 17792bfc5b62f42a9dfbd2ac408e7e71c239330a Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Thu, 29 Jan 2015 17:49:03 +0100 Subject: [PATCH] Properly terminate the array returned by GetLockConflicts(). GetLockConflicts() has for a long time not properly terminated the returned array. During normal processing the returned array is zero initialized which, while not pretty, is sufficient to be recognized as a invalid virtual transaction id. But the HotStandby case is more than aesthetically broken: The allocated (and reused) array is neither zeroed upon allocation, nor reinitialized, nor terminated. Not having a terminating element means that the end of the array will not be recognized and that recovery conflict handling will thus read ahead into adjacent memory. Only terminating when hitting memory content that looks like a invalid virtual transaction id. Luckily this seems so far not have caused significant problems, besides making recovery conflict more expensive. Discussion: 20150127142713.GD29457@awork2.anarazel.de Backpatch into all supported branches. --- src/backend/storage/lmgr/lock.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c index 61c8d216f7..1eb2d4b68d 100644 --- a/src/backend/storage/lmgr/lock.c +++ b/src/backend/storage/lmgr/lock.c @@ -2804,6 +2804,8 @@ GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode) * on this lockable object. */ LWLockRelease(partitionLock); + vxids[count].backendId = InvalidBackendId; + vxids[count].localTransactionId = InvalidLocalTransactionId; return vxids; } @@ -2857,6 +2859,8 @@ GetLockConflicts(const LOCKTAG *locktag, LOCKMODE lockmode) if (count > MaxBackends) /* should never happen */ elog(PANIC, "too many conflicting locks found"); + vxids[count].backendId = InvalidBackendId; + vxids[count].localTransactionId = InvalidLocalTransactionId; return vxids; }