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=-4.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS 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 E2263C43381 for ; Sat, 23 Feb 2019 14:48:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ACED2206A3 for ; Sat, 23 Feb 2019 14:48:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550933338; bh=iglcbKS5NTULXRq/WapoeaKRwlnoPTqOgMISBK4srjM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=dGUVpVSIS7uu7cMNtIbL/SqW7P7nm6XDfG0K1W31GOyy8i5geFYwQiZe+zrrI2jcf 1W0xqcHZe0OmyuHCVco5WEsDap1NX75ghgERElxvuzIjTKsMpuuLoPQ22TWV9c2vKT PNlQYUlSiFuGPmEMNluWcUElzbF4lR/OuLVREoIs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727774AbfBWOs5 (ORCPT ); Sat, 23 Feb 2019 09:48:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:56518 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725859AbfBWOs4 (ORCPT ); Sat, 23 Feb 2019 09:48:56 -0500 Received: from devnote (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 A298620665; Sat, 23 Feb 2019 14:48:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1550933335; bh=iglcbKS5NTULXRq/WapoeaKRwlnoPTqOgMISBK4srjM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=PypviNtiC89kNNGocLqhFShzyUELgismwtA74WTUWqKn/xXSPpEf0ebUmGhGQLhCX 2AqtpbHEeRLK4bqFRSsKrRBJ1namzEd5RAgTXDqr7NCxmfZWsUIpkdndgYKs2KLUfc 7NlPV6UND4oDXGgWrR4Z0g9zNFRp6TF+ucO0IlXo= Date: Sat, 23 Feb 2019 23:48:52 +0900 From: Masami Hiramatsu To: Masami Hiramatsu Cc: Steven Rostedt , linux-kernel@vger.kernel.org, Linus Torvalds , Ingo Molnar , Andrew Morton , stable@vger.kernel.org, Changbin Du Subject: Re: [PATCH 1/2 v2] kprobe: Do not use uaccess functions to access kernel memory that can fault Message-Id: <20190223234852.1a1df1b93ca6045b94c69b26@kernel.org> In-Reply-To: <20190221165252.4a9033b3348f30f9d973dbc4@kernel.org> References: <20190215174712.372898450@goodmis.org> <20190215174945.557218316@goodmis.org> <20190221165252.4a9033b3348f30f9d973dbc4@kernel.org> X-Mailer: Sylpheed 3.5.0 (GTK+ 2.24.30; 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, On Thu, 21 Feb 2019 16:52:52 +0900 Masami Hiramatsu wrote: > > --- > > kernel/trace/trace_kprobe.c | 10 +--------- > > 1 file changed, 1 insertion(+), 9 deletions(-) > > > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > > index d5fb09ebba8b..9eaf07f99212 100644 > > --- a/kernel/trace/trace_kprobe.c > > +++ b/kernel/trace/trace_kprobe.c > > @@ -861,22 +861,14 @@ static const struct file_operations kprobe_profile_ops = { > > static nokprobe_inline int > > fetch_store_strlen(unsigned long addr) > > { > > - mm_segment_t old_fs; > > int ret, len = 0; > > u8 c; > > > > - old_fs = get_fs(); > > - set_fs(KERNEL_DS); > > - pagefault_disable(); > > - BTW, compared with probe_kernel_read() implementation, this function lacks current->kernel_uaccess_faults_ok modification here. I would like to know whether we can avoid this issue if we tweak this flag. Thank you, > > do { > > - ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1); > > + ret = probe_mem_read(&c, (u8 *)addr + len, 1); > > len++; > > } while (c && ret == 0 && len < MAX_STRING_SIZE); > > > > - pagefault_enable(); > > - set_fs(old_fs); > > - > > return (ret < 0) ? ret : len; > > } > > > > -- > > 2.20.1 > > > > > > > -- > Masami Hiramatsu -- Masami Hiramatsu