Remove PushOverrideSearchPath() and PopOverrideSearchPath().

nmisch · nmisch · commit 7c5c4e1c0396 · 2023-07-31T17:04:47.000-07:00
Since commit 681d9e4, they have no in-tree calls. Any new calls would introduce security vulnerabilities like the one fixed in that commit. Alexander Lakhin, reviewed by Aleksander Alekseev. Discussion: https://postgr.es/m/8ffb4650-52c4-6a81-38fc-8f99be981130@gmail.com
diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
@@ -67,9 +67,7 @@
  * may be included:
  *
  * 1. If a TEMP table namespace has been initialized in this session, it
- * is implicitly searched first.  (The only time this doesn't happen is
- * when we are obeying an override search path spec that says not to use the
- * temp namespace, or the temp namespace is included in the explicit list.)
+ * is implicitly searched first.
  *
  * 2. The system catalog namespace is always searched.  If the system
  * namespace is present in the explicit path then it will be searched in
@@ -108,19 +106,14 @@
  * namespace (if it exists), preceded by the user's personal namespace
  * (if one exists).
  *
- * We support a stack of "override" search path settings for use within
- * specific sections of backend code.  namespace_search_path is ignored
- * whenever the override stack is nonempty.  activeSearchPath is always
- * the actually active path; it points either to the search list of the
- * topmost stack entry, or to baseSearchPath which is the list derived
- * from namespace_search_path.
+ * activeSearchPath is always the actually active path; it points to
+ * to baseSearchPath which is the list derived from namespace_search_path.
  *
  * If baseSearchPathValid is false, then baseSearchPath (and other
  * derived variables) need to be recomputed from namespace_search_path.
  * We mark it invalid upon an assignment to namespace_search_path or receipt
  * of a syscache invalidation event for pg_namespace.  The recomputation
- * is done during the next non-overridden lookup attempt.  Note that an
- * override spec is never subject to recomputation.
+ * is done during the next lookup attempt.
  *
  * Any namespaces mentioned in namespace_search_path that are not readable
  * by the current user ID are simply left out of baseSearchPath; so
@@ -161,17 +154,6 @@ static Oid	namespaceUser = InvalidOid;
 /* The above four values are valid only if baseSearchPathValid */
 static bool baseSearchPathValid = true;
 
-/* Override requests are remembered in a stack of OverrideStackEntry structs */
-
-typedef struct
-{
-	List	   *searchPath;		/* the desired search path */
-	Oid			creationNamespace;	/* the desired creation namespace */
-	int			nestLevel;		/* subtransaction nesting level */
-} OverrideStackEntry;
-
-static List *overrideStack = NIL;
-
 /*
  * myTempNamespace is InvalidOid until and unless a TEMP namespace is set up
  * in a particular backend session (this happens when a CREATE TEMP TABLE
@@ -3392,8 +3374,7 @@ SetTempNamespaceState(Oid tempNamespaceId, Oid tempToastNamespaceId)
 
 
 /*
- * GetOverrideSearchPath - fetch current search path definition in form
- * used by PushOverrideSearchPath.
+ * GetOverrideSearchPath - fetch current search path definition.
  *
  * The result structure is allocated in the specified memory context
  * (which might or might not be equal to CurrentMemoryContext); but any
@@ -3512,132 +3493,6 @@ OverrideSearchPathMatchesCurrent(OverrideSearchPath *path)
 	return true;
 }
 
-/*
- * PushOverrideSearchPath - temporarily override the search path
- *
- * Do not use this function; almost any usage introduces a security
- * vulnerability.  It exists for the benefit of legacy code running in
- * non-security-sensitive environments.
- *
- * We allow nested overrides, hence the push/pop terminology.  The GUC
- * search_path variable is ignored while an override is active.
- *
- * It's possible that newpath->useTemp is set but there is no longer any
- * active temp namespace, if the path was saved during a transaction that
- * created a temp namespace and was later rolled back.  In that case we just
- * ignore useTemp.  A plausible alternative would be to create a new temp
- * namespace, but for existing callers that's not necessary because an empty
- * temp namespace wouldn't affect their results anyway.
- *
- * It's also worth noting that other schemas listed in newpath might not
- * exist anymore either.  We don't worry about this because OIDs that match
- * no existing namespace will simply not produce any hits during searches.
- */
-void
-PushOverrideSearchPath(OverrideSearchPath *newpath)
-{
-	OverrideStackEntry *entry;
-	List	   *oidlist;
-	Oid			firstNS;
-	MemoryContext oldcxt;
-
-	/*
-	 * Copy the list for safekeeping, and insert implicitly-searched
-	 * namespaces as needed.  This code should track recomputeNamespacePath.
-	 */
-	oldcxt = MemoryContextSwitchTo(TopMemoryContext);
-
-	oidlist = list_copy(newpath->schemas);
-
-	/*
-	 * Remember the first member of the explicit list.
-	 */
-	if (oidlist == NIL)
-		firstNS = InvalidOid;
-	else
-		firstNS = linitial_oid(oidlist);
-
-	/*
-	 * Add any implicitly-searched namespaces to the list.  Note these go on
-	 * the front, not the back; also notice that we do not check USAGE
-	 * permissions for these.
-	 */
-	if (newpath->addCatalog)
-		oidlist = lcons_oid(PG_CATALOG_NAMESPACE, oidlist);
-
-	if (newpath->addTemp && OidIsValid(myTempNamespace))
-		oidlist = lcons_oid(myTempNamespace, oidlist);
-
-	/*
-	 * Build the new stack entry, then insert it at the head of the list.
-	 */
-	entry = (OverrideStackEntry *) palloc(sizeof(OverrideStackEntry));
-	entry->searchPath = oidlist;
-	entry->creationNamespace = firstNS;
-	entry->nestLevel = GetCurrentTransactionNestLevel();
-
-	overrideStack = lcons(entry, overrideStack);
-
-	/* And make it active. */
-	activeSearchPath = entry->searchPath;
-	activeCreationNamespace = entry->creationNamespace;
-	activeTempCreationPending = false;	/* XXX is this OK? */
-
-	/*
-	 * We always increment activePathGeneration when pushing/popping an
-	 * override path.  In current usage, these actions always change the
-	 * effective path state, so there's no value in checking to see if it
-	 * didn't change.
-	 */
-	activePathGeneration++;
-
-	MemoryContextSwitchTo(oldcxt);
-}
-
-/*
- * PopOverrideSearchPath - undo a previous PushOverrideSearchPath
- *
- * Any push during a (sub)transaction will be popped automatically at abort.
- * But it's caller error if a push isn't popped in normal control flow.
- */
-void
-PopOverrideSearchPath(void)
-{
-	OverrideStackEntry *entry;
-
-	/* Sanity checks. */
-	if (overrideStack == NIL)
-		elog(ERROR, "bogus PopOverrideSearchPath call");
-	entry = (OverrideStackEntry *) linitial(overrideStack);
-	if (entry->nestLevel != GetCurrentTransactionNestLevel())
-		elog(ERROR, "bogus PopOverrideSearchPath call");
-
-	/* Pop the stack and free storage. */
-	overrideStack = list_delete_first(overrideStack);
-	list_free(entry->searchPath);
-	pfree(entry);
-
-	/* Activate the next level down. */
-	if (overrideStack)
-	{
-		entry = (OverrideStackEntry *) linitial(overrideStack);
-		activeSearchPath = entry->searchPath;
-		activeCreationNamespace = entry->creationNamespace;
-		activeTempCreationPending = false;	/* XXX is this OK? */
-	}
-	else
-	{
-		/* If not baseSearchPathValid, this is useless but harmless */
-		activeSearchPath = baseSearchPath;
-		activeCreationNamespace = baseCreationNamespace;
-		activeTempCreationPending = baseTempCreationPending;
-	}
-
-	/* As above, the generation always increments. */
-	activePathGeneration++;
-}
-
-
 /*
  * get_collation_oid - find a collation by possibly qualified name
  *
@@ -3794,10 +3649,6 @@ recomputeNamespacePath(void)
 	bool		pathChanged;
 	MemoryContext oldcxt;
 
-	/* Do nothing if an override search spec is active. */
-	if (overrideStack)
-		return;
-
 	/* Do nothing if path is already valid. */
 	if (baseSearchPathValid && namespaceUser == roleid)
 		return;
@@ -3936,10 +3787,7 @@ recomputeNamespacePath(void)
 
 	/*
 	 * Bump the generation only if something actually changed.  (Notice that
-	 * what we compared to was the old state of the base path variables; so
-	 * this does not deal with the situation where we have just popped an
-	 * override path and restored the prior state of the base path.  Instead
-	 * we rely on the override-popping logic to have bumped the generation.)
+	 * what we compared to was the old state of the base path variables.)
 	 */
 	if (pathChanged)
 		activePathGeneration++;
@@ -4142,29 +3990,6 @@ AtEOXact_Namespace(bool isCommit, bool parallel)
 		myTempNamespaceSubID = InvalidSubTransactionId;
 	}
 
-	/*
-	 * Clean up if someone failed to do PopOverrideSearchPath
-	 */
-	if (overrideStack)
-	{
-		if (isCommit)
-			elog(WARNING, "leaked override search path");
-		while (overrideStack)
-		{
-			OverrideStackEntry *entry;
-
-			entry = (OverrideStackEntry *) linitial(overrideStack);
-			overrideStack = list_delete_first(overrideStack);
-			list_free(entry->searchPath);
-			pfree(entry);
-		}
-		/* If not baseSearchPathValid, this is useless but harmless */
-		activeSearchPath = baseSearchPath;
-		activeCreationNamespace = baseCreationNamespace;
-		activeTempCreationPending = baseTempCreationPending;
-		/* Always bump generation --- see note in recomputeNamespacePath */
-		activePathGeneration++;
-	}
 }
 
 /*
@@ -4179,7 +4004,6 @@ void
 AtEOSubXact_Namespace(bool isCommit, SubTransactionId mySubid,
 					  SubTransactionId parentSubid)
 {
-	OverrideStackEntry *entry;
 
 	if (myTempNamespaceSubID == mySubid)
 	{
@@ -4205,51 +4029,6 @@ AtEOSubXact_Namespace(bool isCommit, SubTransactionId mySubid,
 			MyProc->tempNamespaceId = InvalidOid;
 		}
 	}
-
-	/*
-	 * Clean up if someone failed to do PopOverrideSearchPath
-	 */
-	while (overrideStack)
-	{
-		entry = (OverrideStackEntry *) linitial(overrideStack);
-		if (entry->nestLevel < GetCurrentTransactionNestLevel())
-			break;
-		if (isCommit)
-			elog(WARNING, "leaked override search path");
-		overrideStack = list_delete_first(overrideStack);
-		list_free(entry->searchPath);
-		pfree(entry);
-		/* Always bump generation --- see note in recomputeNamespacePath */
-		activePathGeneration++;
-	}
-
-	/* Activate the next level down. */
-	if (overrideStack)
-	{
-		entry = (OverrideStackEntry *) linitial(overrideStack);
-		activeSearchPath = entry->searchPath;
-		activeCreationNamespace = entry->creationNamespace;
-		activeTempCreationPending = false;	/* XXX is this OK? */
-
-		/*
-		 * It's probably unnecessary to bump generation here, but this should
-		 * not be a performance-critical case, so better to be over-cautious.
-		 */
-		activePathGeneration++;
-	}
-	else
-	{
-		/* If not baseSearchPathValid, this is useless but harmless */
-		activeSearchPath = baseSearchPath;
-		activeCreationNamespace = baseCreationNamespace;
-		activeTempCreationPending = baseTempCreationPending;
-
-		/*
-		 * If we popped an override stack entry, then we already bumped the
-		 * generation above.  If we did not, then the above assignments did
-		 * nothing and we need not bump the generation.
-		 */
-	}
 }
 
 /*
diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
@@ -967,11 +967,6 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 	 * searched anyway.  (Listing pg_catalog explicitly in a non-first
 	 * position would be bad for security.)  Finally add pg_temp to ensure
 	 * that temp objects can't take precedence over others.
-	 *
-	 * Note: it might look tempting to use PushOverrideSearchPath for this,
-	 * but we cannot do that.  We have to actually set the search_path GUC in
-	 * case the extension script examines or changes it.  In any case, the
-	 * GUC_ACTION_SAVE method is just as convenient.
 	 */
 	initStringInfo(&pathbuf);
 	appendStringInfoString(&pathbuf, quote_identifier(schemaName));
diff --git a/src/include/catalog/namespace.h b/src/include/catalog/namespace.h
@@ -167,8 +167,6 @@ extern void ResetTempTableNamespace(void);
 extern OverrideSearchPath *GetOverrideSearchPath(MemoryContext context);
 extern OverrideSearchPath *CopyOverrideSearchPath(OverrideSearchPath *path);
 extern bool OverrideSearchPathMatchesCurrent(OverrideSearchPath *path);
-extern void PushOverrideSearchPath(OverrideSearchPath *newpath);
-extern void PopOverrideSearchPath(void);
 
 extern Oid	get_collation_oid(List *collname, bool missing_ok);
 extern Oid	get_conversion_oid(List *conname, bool missing_ok);
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
@@ -1687,7 +1687,6 @@ OutputPluginCallbacks
 OutputPluginOptions
 OutputPluginOutputType
 OverrideSearchPath
-OverrideStackEntry
 OverridingKind
 PACE_HEADER
 PACL
