Fix another instance of unsafe coding for shm_toc_lookup failure.

tglsfdc · tglsfdc · commit d59ff4ab3111 · 2018-02-02T18:32:05.000-05:00
One or another author of commit 5bcf389 seems to have thought that computing an offset from a NULL pointer would yield another NULL pointer. There may possibly be architectures where that works, but common machines don't work like that. Per a quick code review of places calling shm_toc_lookup and not using noError = false.
diff --git a/src/backend/executor/nodeHash.c b/src/backend/executor/nodeHash.c
@@ -2582,9 +2582,13 @@ ExecHashInitializeWorker(HashState *node, ParallelWorkerContext *pwcxt)
 {
 	SharedHashInfo *shared_info;
 
+	/* might not be there ... */
 	shared_info = (SharedHashInfo *)
 		shm_toc_lookup(pwcxt->toc, node->ps.plan->plan_node_id, true);
-	node->hinstrument = &shared_info->hinstrument[ParallelWorkerNumber];
+	if (shared_info)
+		node->hinstrument = &shared_info->hinstrument[ParallelWorkerNumber];
+	else
+		node->hinstrument = NULL;
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -2582,9 +2582,13 @@ ExecHashInitializeWorker(HashState node, ParallelWorkerContext pwcxt)`
`2582`	`2582`	`{`
`2583`	`2583`	`SharedHashInfo *shared_info;`
`2584`	`2584`
	`2585`	`+ /* might not be there ... */`
`2585`	`2586`	`shared_info = (SharedHashInfo *)`
`2586`	`2587`	`shm_toc_lookup(pwcxt->toc, node->ps.plan->plan_node_id, true);`
`2587`		`- node->hinstrument = &shared_info->hinstrument[ParallelWorkerNumber];`
	`2588`	`+ if (shared_info)`
	`2589`	`+ node->hinstrument = &shared_info->hinstrument[ParallelWorkerNumber];`
	`2590`	`+ else`
	`2591`	`+ node->hinstrument = NULL;`
`2588`	`2592`	`}`
`2589`	`2593`
`2590`	`2594`	`/*`