[mono] Fix a crash during stack trace construction if a this object is null. (#21488)

github-actions[bot] · bholmes · web-flow · commit 6c7e72dd8e0a · 2022-05-24T17:37:26.000+02:00
Fixes dotnet#67354.

Co-authored-by: Bill Holmes &lt;bill.holmes@unity3d.com&gt;
diff --git a/mono/mini/mini-exceptions.c b/mono/mini/mini-exceptions.c
@@ -840,7 +840,7 @@ get_generic_info_from_stack_frame (MonoJitInfo *ji, MonoContext *ctx)
 		/* Avoid returning a managed object */
 		MonoObject *this_obj = (MonoObject *)info;
 
-		return this_obj->vtable;
+		return this_obj ? this_obj->vtable : NULL;
 	}
 }
 
@@ -901,7 +901,7 @@ get_method_from_stack_frame (MonoJitInfo *ji, gpointer generic_info)
 	MonoGenericContext context;
 	MonoMethod *method;
 	
-	if (!ji->has_generic_jit_info || !mono_jit_info_get_generic_jit_info (ji)->has_this)
+	if (!ji->has_generic_jit_info || !mono_jit_info_get_generic_jit_info (ji)->has_this || !generic_info)
 		return jinfo_get_method (ji);
 	context = mono_get_generic_context_from_stack_frame (ji, generic_info);
 

Original file line number	Diff line number	Diff line change
`@@ -840,7 +840,7 @@ get_generic_info_from_stack_frame (MonoJitInfo ji, MonoContext ctx)`
`840`	`840`	`/* Avoid returning a managed object */`
`841`	`841`	`MonoObject this_obj = (MonoObject )info;`
`842`	`842`
`843`		`- return this_obj->vtable;`
	`843`	`+ return this_obj ? this_obj->vtable : NULL;`
`844`	`844`	`}`
`845`	`845`	`}`
`846`	`846`
`@@ -901,7 +901,7 @@ get_method_from_stack_frame (MonoJitInfo *ji, gpointer generic_info)`
`901`	`901`	`MonoGenericContext context;`
`902`	`902`	`MonoMethod *method;`
`903`	`903`
`904`		`- if (!ji->has_generic_jit_info \|\| !mono_jit_info_get_generic_jit_info (ji)->has_this)`
	`904`	`+ if (!ji->has_generic_jit_info \|\| !mono_jit_info_get_generic_jit_info (ji)->has_this \|\| !generic_info)`
`905`	`905`	`return jinfo_get_method (ji);`
`906`	`906`	`context = mono_get_generic_context_from_stack_frame (ji, generic_info);`
`907`	`907`