Avoid possible longjmp-induced logic error in PLy_trigger_build_args.

tglsfdc · tglsfdc · commit 5eac8cef2454 · 2024-04-01T15:15:03.000-04:00
The "pltargs" variable wasn't marked volatile, which makes it unsafe to change its value within the PG_TRY block. It looks like the worst outcome would be to fail to release a refcount on Py_None during an (improbable) error exit, which would likely go unnoticed in the field. Still, it's a bug. A one-liner fix could be to mark pltargs volatile, but on the whole it seems cleaner to arrange things so that we don't change its value within PG_TRY. Per report from Xing Guo. This has been there for quite awhile, so back-patch to all supported branches. Discussion: https://postgr.es/m/CACpMh+DLrk=fDv07MNpBT4J413fDAm+gmMXgi8cjPONE+jvzuw@mail.gmail.com
diff --git a/src/pl/plpython/plpy_exec.c b/src/pl/plpython/plpy_exec.c
@@ -689,7 +689,7 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure *proc, HeapTuple *r
 			   *pltrelid,
 			   *plttablename,
 			   *plttableschema,
-			   *pltargs = NULL,
+			   *pltargs,
 			   *pytnew,
 			   *pytold,
 			   *pltdata;
@@ -713,6 +713,11 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure *proc, HeapTuple *r
 			return NULL;
 		}
 	}
+	else
+	{
+		Py_INCREF(Py_None);
+		pltargs = Py_None;
+	}
 
 	PG_TRY();
 	{
@@ -856,7 +861,7 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure *proc, HeapTuple *r
 			PyObject   *pltarg;
 
 			/* pltargs should have been allocated before the PG_TRY block. */
-			Assert(pltargs);
+			Assert(pltargs && pltargs != Py_None);
 
 			for (i = 0; i < tdata->tg_trigger->tgnargs; i++)
 			{
@@ -870,8 +875,7 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure *proc, HeapTuple *r
 		}
 		else
 		{
-			Py_INCREF(Py_None);
-			pltargs = Py_None;
+			Assert(pltargs == Py_None);
 		}
 		PyDict_SetItemString(pltdata, "args", pltargs);
 		Py_DECREF(pltargs);

Original file line number	Diff line number	Diff line change
`@@ -689,7 +689,7 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure proc, HeapTuple r`
`689`	`689`	`*pltrelid,`
`690`	`690`	`*plttablename,`
`691`	`691`	`*plttableschema,`
`692`		`- *pltargs = NULL,`
	`692`	`+ *pltargs,`
`693`	`693`	`*pytnew,`
`694`	`694`	`*pytold,`
`695`	`695`	`*pltdata;`
`@@ -713,6 +713,11 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure proc, HeapTuple r`
`713`	`713`	`return NULL;`
`714`	`714`	`}`
`715`	`715`	`}`
	`716`	`+ else`
	`717`	`+ {`
	`718`	`+ Py_INCREF(Py_None);`
	`719`	`+ pltargs = Py_None;`
	`720`	`+ }`
`716`	`721`
`717`	`722`	`PG_TRY();`
`718`	`723`	`{`
`@@ -856,7 +861,7 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure proc, HeapTuple r`
`856`	`861`	`PyObject *pltarg;`
`857`	`862`
`858`	`863`	`/* pltargs should have been allocated before the PG_TRY block. */`
`859`		`- Assert(pltargs);`
	`864`	`+ Assert(pltargs && pltargs != Py_None);`
`860`	`865`
`861`	`866`	`for (i = 0; i < tdata->tg_trigger->tgnargs; i++)`
`862`	`867`	`{`
`@@ -870,8 +875,7 @@ PLy_trigger_build_args(FunctionCallInfo fcinfo, PLyProcedure proc, HeapTuple r`
`870`	`875`	`}`
`871`	`876`	`else`
`872`	`877`	`{`
`873`		`- Py_INCREF(Py_None);`
`874`		`- pltargs = Py_None;`
	`878`	`+ Assert(pltargs == Py_None);`
`875`	`879`	`}`
`876`	`880`	`PyDict_SetItemString(pltdata, "args", pltargs);`
`877`	`881`	`Py_DECREF(pltargs);`