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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 0C525C433E2 for ; Wed, 20 May 2020 11:11:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D25B7207D3 for ; Wed, 20 May 2020 11:11:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589973094; bh=CZO2oVmSFplMBz9Hp/Ib++cLu93ut1vlEwhwSgDctvg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=lIlsO2yu/F02rXO8n5C9fHB4KjxMe7LUSoXmJd9eE8XCopZVzjOE72oVxlPHglCPS Vwh5laiBVlWg30ZcM4PCNVv1/EcydZo4LO+qCajDl5X2/C+Un9o7nX/UVy4DIsTX7k NrflsN1Knp5ooWLpaTpKWNHIn7WcQIA/tD0RZbHg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726868AbgETLLe (ORCPT ); Wed, 20 May 2020 07:11:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:56474 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726859AbgETLLc (ORCPT ); Wed, 20 May 2020 07:11:32 -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 6429E207C4; Wed, 20 May 2020 11:11:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589973091; bh=CZO2oVmSFplMBz9Hp/Ib++cLu93ut1vlEwhwSgDctvg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0JQBodzpZZsofv0Hjk8g+YCto+yzr1HnJmp8bkaaHFsZdNStcwkqu6sxB/Cq7RGNZ D9oyW+ivG0VvZVxdbnNjqnjrKg4ZFxKYuPou20DYf2dxIBIfJoUskwUkakdJdMZzgW O2b3pTDEl9xo3o3HjCuYb8IrGfvnz8+E0HAxmEdI= Date: Wed, 20 May 2020 20:11:26 +0900 From: Masami Hiramatsu To: Christoph Hellwig Cc: x86@kernel.org, Alexei Starovoitov , Daniel Borkmann , Linus Torvalds , Andrew Morton , linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 13/20] maccess: always use strict semantics for probe_kernel_read Message-Id: <20200520201126.f37d3b1e46355199216404e2@kernel.org> In-Reply-To: <20200519134449.1466624-14-hch@lst.de> References: <20200519134449.1466624-1-hch@lst.de> <20200519134449.1466624-14-hch@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=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Tue, 19 May 2020 15:44:42 +0200 Christoph Hellwig wrote: > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 2f6737cc53e6c..82da20e712507 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -1208,7 +1208,13 @@ fetch_store_strlen(unsigned long addr) > u8 c; > > do { > - ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > + if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) && > + (unsigned long)addr < TASK_SIZE) { > + ret = probe_user_read(&c, > + (__force u8 __user *)addr + len, 1); > + } else { > + ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > + } > len++; > } while (c && ret == 0 && len < MAX_STRING_SIZE); To avoid redundant check in the loop, we can use strnlen_user_nofault() out of the loop. Something like below. ... u8 c; if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) && (unsigned long)addr < TASK_SIZE) { return strnlen_user_nofault((__force u8 __user *)addr, MAX_STRING_SIZE); do { ret = probe_kernel_read(&c, (u8 *)addr + len, 1); len++; } while (c && ret == 0 && len < MAX_STRING_SIZE); ... This must work because we must not have a string that continues across kernel　space and user space. Thank you, -- Masami Hiramatsu