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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3B29FC3DA45 for ; Wed, 10 Jul 2024 12:12:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Mj4rPGlzU3KDI9Lkv3uEFfQ8B0n2Zr03a46AYuDf6R4=; b=nAeTDykaWzcDJpPMpEg6t63zxO Ix8jrbkq0un3VohC13mdwtCmV4JO5XYWwDcYxJvO3LvoJrK9npOBwn5iu5X+vWSXbL74ywyE71T/d 8hGRrQXoViP/9ayNCNPB6ZucABImq2FSWAhlF3W7KBBIlZv6l+VRS5fk6uU6YLUNgF2/FGRhGqRTG P+rOntbpIsLluCknyzrarsqIUaM4OlWdAWlIAASBFn7geDEP9X6ZX+sRjogfihw9ZXlVRvcu9CV6E TxRhWW+Jy8bb1Ybbmy+XAxG7shj7J0vDqHtzJuYP9wORRS+0uRQiCrpyJnyiUXg+tVu9XSvn0Jbft itb0hsyA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sRWAy-0000000ASWw-2uxY; Wed, 10 Jul 2024 12:12:00 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sRWAh-0000000ASTG-38As for linux-arm-kernel@lists.infradead.org; Wed, 10 Jul 2024 12:11:45 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 9D53461A5E; Wed, 10 Jul 2024 12:11:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28241C32781; Wed, 10 Jul 2024 12:11:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720613502; bh=UurvNuYtwMtcWIKDARRq2Bnik8U4B3mY3wKPG7xV4pw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=F6NZWUFu/No8NTOvvKb9LYVm32TiEC6YfZzQ9rP66+C3t7gEebuNCb3g5czsNx0Ad d1O30QXUgaGuUYzLpkwAoDbQILVIBFAGKjEpFQpTXmnXd9cwkfqWO3ZNa/1dciMmaH 8MbuG4EA+vrFHpnTouhbDTdYyzpk6si8juUcPqS/sVjIXdLVMz8ThDvevCcDlncBqR MuCTxJ9S0mZnJA9H7CPG/DYoy0Dh7FF0DPtJzf8mEHaRlMwA1B4oA8c1BnTXK6dwKD EjyDoFRhPdMLRczBYepjDVr0I2YSxxmNQmrZN+VcdXeaDcPCg8g5IUNOTm3PUi/ww7 32Ku/8xQDr+lQ== Date: Wed, 10 Jul 2024 13:11:36 +0100 From: Will Deacon To: Tiezhu Yang Cc: Mark Rutland , Russell King , Catalin Marinas , Oleg Nesterov , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/3] arm64: hw_breakpoint: Save privilege of access control via ptrace Message-ID: <20240710121136.GA14080@willie-the-truck> References: <20240709095506.9691-1-yangtiezhu@loongson.cn> <20240709095506.9691-4-yangtiezhu@loongson.cn> <20240709100515.GB12978@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240710_051143_854681_0E508AB5 X-CRM114-Status: GOOD ( 17.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jul 09, 2024 at 08:07:50PM +0800, Tiezhu Yang wrote: > On 07/09/2024 06:05 PM, Will Deacon wrote: > > On Tue, Jul 09, 2024 at 05:55:06PM +0800, Tiezhu Yang wrote: > > > diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c > > > index 0d022599eb61..3b37c4a2e0d4 100644 > > > --- a/arch/arm64/kernel/ptrace.c > > > +++ b/arch/arm64/kernel/ptrace.c > > > @@ -309,6 +309,7 @@ static struct perf_event *ptrace_hbp_create(unsigned int note_type, > > > attr.bp_addr = 0; > > > attr.bp_len = HW_BREAKPOINT_LEN_4; > > > attr.bp_type = type; > > > + attr.bp_priv = AARCH64_BREAKPOINT_EL0; > > > attr.disabled = 1; > > > > > > bp = register_user_hw_breakpoint(&attr, ptrace_hbptriggered, NULL, tsk); > > > @@ -352,6 +353,7 @@ static int ptrace_hbp_fill_attr_ctrl(unsigned int note_type, > > > attr->bp_len = len; > > > attr->bp_type = type; > > > attr->bp_addr += offset; > > > + attr->bp_priv = ctrl.privilege; > > > > Wait, so ptrace can now set breakpoints with arbitrary privileges? > > The ptrace user should make sure the privilege is correct. > For example, the privilege is set as el0 > in aarch64_point_encode_ctrl_reg() of GDB: > > /* enabled at el0 */ > ctrl |= (2 << 1) | 1; > > https://sourceware.org/git/?p=binutils-gdb.git;a=blob;f=gdb/nat/aarch64-hw-point.c#l135 We shouldn't rely on userspace behaving correctly when dealing with privilege levels. Will