postgres.git / summary / log / commit / refs

commit    701dcc983eb4d08dd36bb3a0ddba255819797760
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Mon Mar 30 17:05:27 2015 +0000

    Fix rare core dump in BackendIdGetTransactionIds().
    
    BackendIdGetTransactionIds() neglected the possibility that the PROC
    pointer in a ProcState array entry is null.  In current usage, this could
    only crash if the other backend had exited since pgstat_read_current_status
    saw it as active, which is a pretty narrow window.  But it's reachable in
    the field, per bug #12918 from Vladimir Borodin.
    
    Back-patch to 9.4 where the faulty code was introduced.


 src/backend/storage/ipc/sinvaladt.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/backend/storage/ipc/sinvaladt.c b/src/backend/storage/ipc/sinvaladt.c
index 81b85c0e420..a2fde89b526 100644
--- a/src/backend/storage/ipc/sinvaladt.c
+++ b/src/backend/storage/ipc/sinvaladt.c
@@ -403,9 +403,7 @@ BackendIdGetProc(int backendID)
 void
 BackendIdGetTransactionIds(int backendID, TransactionId *xid, TransactionId *xmin)
 {
-	ProcState  *stateP;
 	SISeg	   *segP = shmInvalBuffer;
-	PGXACT	   *xact;
 
 	*xid = InvalidTransactionId;
 	*xmin = InvalidTransactionId;
@@ -415,11 +413,16 @@ BackendIdGetTransactionIds(int backendID, TransactionId *xid, TransactionId *xmi
 
 	if (backendID > 0 && backendID <= segP->lastBackend)
 	{
-		stateP = &segP->procState[backendID - 1];
-		xact = &ProcGlobal->allPgXact[stateP->proc->pgprocno];
+		ProcState  *stateP = &segP->procState[backendID - 1];
+		PGPROC	   *proc = stateP->proc;
 
-		*xid = xact->xid;
-		*xmin = xact->xmin;
+		if (proc != NULL)
+		{
+			PGXACT	   *xact = &ProcGlobal->allPgXact[proc->pgprocno];
+
+			*xid = xact->xid;
+			*xmin = xact->xmin;
+		}
 	}
 
 	LWLockRelease(SInvalWriteLock);


[parent: 0633a60f4d2a]