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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 D1D1BC433E0 for ; Fri, 5 Jun 2020 16:58:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD016207D8 for ; Fri, 5 Jun 2020 16:58:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591376292; bh=Hz2cNhIpYpdNkmGN9wbmQIv+M+zaCSAsbSR9oMK5DvU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=wiCoRkcPyCbU+dPXf4JPRasHLDpBjBKFjegCydB1x+X+Ex4Xn7XTPNCBRFA7qjP5W ss3c4/uy9TiQUa4DBaAe9RPIo1w02dfOGZ5GRsYu7WA+ZFJL2U6R5e7s3uEJXmRA8y Z3mI6Xry+vBPKVCYrwZeU1kcVPAFrIdnWsB4ixz0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726614AbgFEQ6L (ORCPT ); Fri, 5 Jun 2020 12:58:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:51476 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbgFEQ6L (ORCPT ); Fri, 5 Jun 2020 12:58:11 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 52F542077D; Fri, 5 Jun 2020 16:58:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591376290; bh=Hz2cNhIpYpdNkmGN9wbmQIv+M+zaCSAsbSR9oMK5DvU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=SKxg7oWuUjrWiWfeycoMHpCJ6lMCCcTeSRmH+LRDwApuH8pvTlLIwuL7Hu5pRX9WH lUJWXHWbbN8PjeqI7+UqL5yS5pMibuqbxqloRxwjMu8yAMIPr+czrEQ6sK8l+sSgND 7AK5vy0t4mH0TDHQdZHfgMEjhNihzwdowt3lHteM= Date: Sat, 6 Jun 2020 01:58:06 +0900 From: Masami Hiramatsu To: Christoph Hellwig Cc: Sven Schnelle , linux-kernel@vger.kernel.org, Masami Hiramatsu Subject: Re: kprobes string reading broken on s390 Message-Id: <20200606015806.c8f9cafc3c6c52b8854d6cd3@kernel.org> In-Reply-To: <20200605132541.GB31829@lst.de> References: <20200605110533.GA57038@tuxmaker.boeblingen.de.ibm.com> <20200605132541.GB31829@lst.de> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sven, On Fri, 5 Jun 2020 15:25:41 +0200 Christoph Hellwig wrote: > Yes, this looks correct. You probably want to write a small changelog > and add a Fixes tag, though. > > On Fri, Jun 05, 2020 at 01:05:34PM +0200, Sven Schnelle wrote: > > Hi Christoph, > > > > with the latest linux-next i noticed that some tests in the > > ftrace test suites are failing on s390, namely: > > > > [FAIL] Kprobe event symbol argument > > [FAIL] Kprobe event with comm arguments > > > > The following doesn't work anymore: > > > > cd /sys/kernel/tracing > > echo 'p:testprobe _do_fork comm=$comm ' >kprobe_events > > echo 1 >/sys/kernel/tracing/events/kprobes/testprobe/enable > > cat /sys/kernel/tracing/trace > > > > it will just show > > > > test.sh-519 [012] .... 18.580625: testprobe: (_do_fork+0x0/0x3c8) comm=(fault) > > > > Looking at d411a9c4e95a ("tracing/kprobes: handle mixed kernel/userspace probes > > better") i see that there are two helpers for reading strings: > > > > fetch_store_string_user() -> read string from user space > > fetch_store_string() -> read string from kernel space(?) > > > > but in the end both are using strncpy_from_user_nofault(), but i would > > think that fetch_store_string() should use strncpy_from_kernel_nofault(). > > However, i'm not sure about the exact semantics of fetch_store_string(), > > as there where a lot of wrong assumptions in the past, especially since > > on x86 you usually don't fail if you use the same function for accessing kernel > > and userspace although it's technically wrong. Thanks for fixing! This report can be a good changelog. Please resend it with Fixed tag as Christoph said. Christoph, it seems your series in the akpm tree, so this also should be sent to Andrew? Thank you, > > > > Regards, > > Sven > > > > commit 81408eab8fcc79dc0871a95462b13176d3446f5e > > Author: Sven Schnelle > > Date: Fri Jun 5 13:01:24 2020 +0200 > > > > kprobes: use strncpy_from_kernel_nofault() in fetch_store_string() > > > > Signed-off-by: Sven Schnelle > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > index b1f21d558e45..ea8d0b094f1b 100644 > > --- a/kernel/trace/trace_kprobe.c > > +++ b/kernel/trace/trace_kprobe.c > > @@ -1278,7 +1278,7 @@ fetch_store_string(unsigned long addr, void *dest, void *base) > > * Try to get string again, since the string can be changed while > > * probing. > > */ > > - ret = strncpy_from_user_nofault(__dest, (void *)addr, maxlen); > > + ret = strncpy_from_kernel_nofault(__dest, (void *)addr, maxlen); > > if (ret >= 0) > > *(u32 *)dest = make_data_loc(ret, __dest - base); > > > ---end quoted text--- -- Masami Hiramatsu