From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E3E86C433E0 for ; Sun, 7 Mar 2021 21:15:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD9A165155 for ; Sun, 7 Mar 2021 21:15:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233014AbhCGVO6 (ORCPT ); Sun, 7 Mar 2021 16:14:58 -0500 Received: from mail.kernel.org ([198.145.29.99]:59740 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231397AbhCGVOk (ORCPT ); Sun, 7 Mar 2021 16:14:40 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 380A965155; Sun, 7 Mar 2021 21:14:39 +0000 (UTC) Date: Sun, 7 Mar 2021 16:14:37 -0500 From: Steven Rostedt To: Peter Chen Cc: Pawel Laszczak , Linus Torvalds , Linux Kernel Mailing List , Ingo Molnar , Andrew Morton , Masami Hiramatsu , Jacob Wen , Felipe Balbi , Greg KH Subject: Re: [PATCH 0/2] tracing: Detect unsafe dereferencing of pointers from trace events Message-ID: <20210307161437.4c00cd4a@gandalf.local.home> In-Reply-To: <20210307040142.GA2930@b29397-desktop> References: <20210226185909.100032746@goodmis.org> <20210227141802.5c9aca91@oasis.local.home> <20210227190831.56956c80@oasis.local.home> <20210302082355.GA8633@nchen> <20210302095605.7b2881cd@gandalf.local.home> <20210307040142.GA2930@b29397-desktop> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 7 Mar 2021 12:01:42 +0800 Peter Chen wrote: > On 21-03-02 09:56:05, Steven Rostedt wrote: > > On Tue, 2 Mar 2021 16:23:55 +0800 > > Peter Chen wrote: > > > > s it looks like it uses %pa which IIUC from the printk code, it > > > > >> dereferences the pointer to find it's virtual address. The event has > > > > >> this as the field: > > > > >> > > > > >> __field(struct cdns3_trb *, start_trb_addr) > > > > >> > > > > >> Assigns it with: > > > > >> > > > > >> __entry->start_trb_addr = req->trb; > > > > >> > > > > >> And prints that with %pa, which will dereference pointer at the time of > > > > >> reading, where the address in question may no longer be around. That > > > > >> looks to me as a potential bug. > > > > > > Steven, thanks for reporting. Do you mind sending patch to fix it? > > > If you have no time to do it, I will do it later. > > > > > > > I would have already fixed it, but I wasn't exactly sure how this is used. > > > > In Documentation/core-api/printk-formats.rst we have: > > > > Physical address types phys_addr_t > > ---------------------------------- > > > > :: > > > > %pa[p] 0x01234567 or 0x0123456789abcdef > > > > For printing a phys_addr_t type (and its derivatives, such as > > resource_size_t) which can vary based on build options, regardless of the > > width of the CPU data path. > > > > So it only looks like it is used to for the size of the pointer. > > > > I guess something like this might work: > > > > diff --git a/drivers/usb/cdns3/cdns3-trace.h b/drivers/usb/cdns3/cdns3-trace.h > > index 8648c7a7a9dd..d3b8624fc427 100644 > > --- a/drivers/usb/cdns3/cdns3-trace.h > > +++ b/drivers/usb/cdns3/cdns3-trace.h > > @@ -214,7 +214,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request, > > __field(int, no_interrupt) > > __field(int, start_trb) > > __field(int, end_trb) > > - __field(struct cdns3_trb *, start_trb_addr) > > + __field(phys_addr_t, start_trb_addr) > > __field(int, flags) > > __field(unsigned int, stream_id) > > ), > > @@ -230,7 +230,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request, > > __entry->no_interrupt = req->request.no_interrupt; > > __entry->start_trb = req->start_trb; > > __entry->end_trb = req->end_trb; > > - __entry->start_trb_addr = req->trb; > > + __entry->start_trb_addr = *(const phys_addr_t *)req->trb; > > __entry->flags = req->flags; > > __entry->stream_id = req->request.stream_id; > > ), > > @@ -244,7 +244,7 @@ DECLARE_EVENT_CLASS(cdns3_log_request, > > __entry->status, > > __entry->start_trb, > > __entry->end_trb, > > - __entry->start_trb_addr, > > + /* %pa dereferences */ &__entry->start_trb_addr, > > __entry->flags, > > __entry->stream_id > > ) > > > > > > Can you please test it? I don't have the hardware, but I also want to make > > sure I don't break anything. > > > > Thanks, > > > > Since the virtual address for req->trb is NULL before using it. It will > trigger below oops using your change. There is already index > (start_trb/end_trb) for which TRB it has handled, it is not necessary > to trace information for its physical address. I decide to delete this > trace entry, thanks for reporting it. Thanks for fixing / removing it. But I should have added a NULL check before dereferencing, because that's what the vsnprintf() code does. -- Steve