On Tue, 27 Jun 2023 23:33:06 +0900 Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> wrote: > > diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c > > index 18d36842faf5..0121e8c0d54e 100644 > > --- a/kernel/trace/fprobe.c > > +++ b/kernel/trace/fprobe.c > > @@ -364,19 +364,13 @@ int unregister_fprobe(struct fprobe *fp) > > fp->ops.saved_func != fprobe_kprobe_handler)) > > return -EINVAL; > > > > - /* > > - * rethook_free() starts disabling the rethook, but the rethook handlers > > - * may be running on other processors at this point. To make sure that all > > - * current running handlers are finished, call unregister_ftrace_function() > > - * after this. > > - */ Oh, wait, here is an important comment. If a rethook handler is still running (because it hooks target function exit), returning from unregister_fprobe() right after rethook_free() may cause another issue. rethook_free() clears 'rh->handler', so after calling rethook_free(), we can ensure no NEW rethook handler (means fprobe_exit_handler()) is called. However, it doesn't mean there is no current running fprobe_exit_handler(). Thus if unregister_fprobe() caller releases the 'fp' right after returning from unregister_fprobe(), current running fprobe_exit_handler() can access 'fp' (use-after-free). Thus we need to add below code with this patch; /* * The rethook handlers may be running on other processors at this point. * To make sure that all current running handlers are finished, disable * rethook by clearing handler and call unregister_ftrace_function() * to ensure all running rethook handlers exit. And call rethook_free(). */ if (fp->rethook) WRITE_ONCE(fp->rethook->handler, NULL); > > - if (fp->rethook) > > - rethook_free(fp->rethook); > > - > > ret = unregister_ftrace_function(&fp->ops); > > if (ret < 0) > > return ret; > > > > + if (fp->rethook) > > + rethook_free(fp->rethook); > > + > > ftrace_free_filter(&fp->ops); > > > > return ret; Thank you, > > -- > > 2.40.1 > > > > > -- > Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
