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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (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 CBB49C433FE for ; Fri, 4 Nov 2022 13:13:16 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4N3gzb1DvZz3f43 for ; Sat, 5 Nov 2022 00:13:15 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) by lists.ozlabs.org (Postfix) with ESMTP id 4N3gyw374Mz3c4B for ; Sat, 5 Nov 2022 00:12:38 +1100 (AEDT) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id 2A4DATlX011527; Fri, 4 Nov 2022 08:10:29 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id 2A4DAT2Z011522; Fri, 4 Nov 2022 08:10:29 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 4 Nov 2022 08:10:28 -0500 From: Segher Boessenkool To: Nicholas Piggin Subject: Re: [RFC PATCH 01/19] powerpc/perf: callchain validate kernel stack pointer bounds Message-ID: <20221104131028.GN25951@gate.crashing.org> References: <20221031055440.3594315-1-npiggin@gmail.com> <20221031055440.3594315-2-npiggin@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221031055440.3594315-2-npiggin@gmail.com> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Oct 31, 2022 at 03:54:22PM +1000, Nicholas Piggin wrote: > Could the user set r1 to be equal to the address matching the first > interrupt frame - STACK_INT_FRAME_SIZE, which is in the previous page > due to the kernel redzone, and induce the kernel to load the marker from > there? Possibly it could cause a crash at least. Yes, the user can set r1 to anything, it is just a general purpose register. This isn't a valid thing to do of course, the ABI requires r1 to point at a valid stack at all times, but it is an obvious attack point if we do not harden against this :-) Segher