postgres.git / summary / log / commit / refs

commit    eed5bbc48026976444dc020086559acc8e6f26ca
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Sun Sep 20 20:48:44 2015 +0000
First released in: 9.6.0, 9.0.23, 9.1.19, 9.2.14, 9.3.10, 9.4.5, 9.5.0

    Be more wary about partially-valid LOCALLOCK data in RemoveLocalLock().
    
    RemoveLocalLock() must consider the possibility that LockAcquireExtended()
    failed to palloc the initial space for a locallock's lockOwners array.
    I had evidently meant to cope with this hazard when the code was originally
    written (commit 1785acebf2ed14fd66955e2d9a55d77a025f418d), but missed that
    the pfree needed to be protected with an if-test.  Just to make sure things
    are left in a clean state, reset numLockOwners as well.
    
    Per low-memory testing by Andreas Seltenreich.  Back-patch to all supported
    branches.


 src/backend/storage/lmgr/lock.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/backend/storage/lmgr/lock.c b/src/backend/storage/lmgr/lock.c
index 8b5dcb82a81..77de95d3593 100644
--- a/src/backend/storage/lmgr/lock.c
+++ b/src/backend/storage/lmgr/lock.c
@@ -644,7 +644,7 @@ LockAcquireExtended(const LOCKTAG *locktag,
 		locallock->nLocks = 0;
 		locallock->numLockOwners = 0;
 		locallock->maxLockOwners = 8;
-		locallock->lockOwners = NULL;
+		locallock->lockOwners = NULL;	/* in case next line fails */
 		locallock->lockOwners = (LOCALLOCKOWNER *)
 			MemoryContextAlloc(TopMemoryContext,
 						  locallock->maxLockOwners * sizeof(LOCALLOCKOWNER));
@@ -994,8 +994,11 @@ LockAcquireExtended(const LOCKTAG *locktag,
 static void
 RemoveLocalLock(LOCALLOCK *locallock)
 {
-	pfree(locallock->lockOwners);
+	locallock->numLockOwners = 0;
+	if (locallock->lockOwners != NULL)
+		pfree(locallock->lockOwners);
 	locallock->lockOwners = NULL;
+
 	if (!hash_search(LockMethodLocalHash,
 					 (void *) &(locallock->tag),
 					 HASH_REMOVE, NULL))


[parent: 44297a058ea0]