From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Schmitz Subject: Re: [PATCH 08/10] parisc: fix livelock in uaccess Date: Wed, 1 Mar 2023 08:18:59 +1300 Message-ID: References: <20230228152236.GA4088022@roeck-us.net> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1677611948; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=FpEVz7SmprPoPkB0vfE/PqJxuugSFBKj6AY2r5uLAhc=; b=oWlcXRzyqWqEIYwyzrAbhH5dfbtnZIzo1YdAD6EbxrkG1UYmywauWswlbWUb9RyzJT brrhvXg9BV/J80dlhPlO1Y21wLf6vRkFdXy7JICIvDrelyzHIZjZVwrR4yuaicL7f3Vk 2p3merJr6M4IafXoXz51BvBxgjw+2vFOvA7iQCX7+ipsnTqqyjWJ3THXEnrQ8p4gJgDk xZ3DYrEnn6dh5SSFWIpnSPW533U6fF1NRXuZZhGMXkF858tTyzkALowN2hKgVfeUNsrR 5wS/6VMndefgSb0UUhYGxgiYLa81lYWrHHI0iDazPBKk+F/PHzqrgvgcgWVcBnyOqxfC HgLQ== Content-Language: en-US In-Reply-To: <20230228152236.GA4088022@roeck-us.net> List-ID: Content-Type: text/plain; charset="utf-8"; format="flowed" To: Guenter Roeck , Al Viro Cc: linux-arch@vger.kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org, Michal Simek , Dinh Nguyen , openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, sparclinux@vger.kernel.org, Linus Torvalds Guenter, On 1/03/23 04:22, Guenter Roeck wrote: > On Tue, Jan 31, 2023 at 08:06:27PM +0000, Al Viro wrote: >> parisc equivalent of 26178ec11ef3 "x86: mm: consolidate VM_FAULT_RETRY handling" >> If e.g. get_user() triggers a page fault and a fatal signal is caught, we might >> end up with handle_mm_fault() returning VM_FAULT_RETRY and not doing anything >> to page tables. In such case we must *not* return to the faulting insn - >> that would repeat the entire thing without making any progress; what we need >> instead is to treat that as failed (user) memory access. >> >> Signed-off-by: Al Viro >> --- >> arch/parisc/mm/fault.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c >> index 869204e97ec9..bb30ff6a3e19 100644 >> --- a/arch/parisc/mm/fault.c >> +++ b/arch/parisc/mm/fault.c >> @@ -308,8 +308,11 @@ void do_page_fault(struct pt_regs *regs, unsigned long code, >> >> fault = handle_mm_fault(vma, address, flags, regs); >> >> - if (fault_signal_pending(fault, regs)) >> + if (fault_signal_pending(fault, regs)) { >> + if (!user_mode(regs)) >> + goto no_context; > 0-day rightfully complains that this leaves 'msg' uninitialized. > > arch/parisc/mm/fault.c:427 do_page_fault() error: uninitialized symbol 'msg' > > Guenter What happens if you initialize msg to "Page fault: no context" right at the start of do_page_fault (and drop the assignment a few lines down as that's now redundant)? (Wondering if the zero page access on parisc could cause a trip right back into do_page_fault, ad infinitum...) Cheers,     Michael >> return; >> + } >> >> /* The fault is fully completed (including releasing mmap lock) */ >> if (fault & VM_FAULT_COMPLETED) From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Schmitz Date: Tue, 28 Feb 2023 19:18:59 +0000 Subject: Re: [PATCH 08/10] parisc: fix livelock in uaccess Message-Id: List-Id: References: <20230228152236.GA4088022@roeck-us.net> In-Reply-To: <20230228152236.GA4088022@roeck-us.net> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Guenter Roeck , Al Viro Cc: linux-arch@vger.kernel.org, linux-alpha@vger.kernel.org, linux-ia64@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-m68k@lists.linux-m68k.org, Michal Simek , Dinh Nguyen , openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, sparclinux@vger.kernel.org, Linus Torvalds Guenter, On 1/03/23 04:22, Guenter Roeck wrote: > On Tue, Jan 31, 2023 at 08:06:27PM +0000, Al Viro wrote: >> parisc equivalent of 26178ec11ef3 "x86: mm: consolidate VM_FAULT_RETRY handling" >> If e.g. get_user() triggers a page fault and a fatal signal is caught, we might >> end up with handle_mm_fault() returning VM_FAULT_RETRY and not doing anything >> to page tables. In such case we must *not* return to the faulting insn - >> that would repeat the entire thing without making any progress; what we need >> instead is to treat that as failed (user) memory access. >> >> Signed-off-by: Al Viro >> --- >> arch/parisc/mm/fault.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c >> index 869204e97ec9..bb30ff6a3e19 100644 >> --- a/arch/parisc/mm/fault.c >> +++ b/arch/parisc/mm/fault.c >> @@ -308,8 +308,11 @@ void do_page_fault(struct pt_regs *regs, unsigned long code, >> >> fault = handle_mm_fault(vma, address, flags, regs); >> >> - if (fault_signal_pending(fault, regs)) >> + if (fault_signal_pending(fault, regs)) { >> + if (!user_mode(regs)) >> + goto no_context; > 0-day rightfully complains that this leaves 'msg' uninitialized. > > arch/parisc/mm/fault.c:427 do_page_fault() error: uninitialized symbol 'msg' > > Guenter What happens if you initialize msg to "Page fault: no context" right at the start of do_page_fault (and drop the assignment a few lines down as that's now redundant)? (Wondering if the zero page access on parisc could cause a trip right back into do_page_fault, ad infinitum...) Cheers,     Michael >> return; >> + } >> >> /* The fault is fully completed (including releasing mmap lock) */ >> if (fault & VM_FAULT_COMPLETED) 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 BFBE4C64EC7 for ; Tue, 28 Feb 2023 19:19:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=lMrSUj7T5YBwYQD0TjyYDfmAL6Wl/Yg3QGIlEDwg29Q=; b=RXaruToOYXDKbo pq/FqmdQ+gNu2B58/ONfMhgqrv91pPbqBy0z9XdpLFrwRXpOF7GrJXBHliRYRdfD1edB8unSTDLYu UxI3itw/uKuQcg8cm+hJMb0HRrWb54VYGCVatkVI1UBA255l78mfQ8EwLrZABUHRrHS5ZvNCphFru vx5RkfR7zJHnTccYREYfA10k5XDqyXwMOxB/9t2jCGwVZ6wmpBobZhePO4/msFVj4fH9oy0eAXj1c JK5JrFFf2nSykzPXcxtKRXwGR9JoizCsoQZU1Azp0vXfAZVxUOlBieRBECl2OhfdaEBxue9zsmgQ/ 6QJB1oMOvEdhnOIzW17g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pX5VN-00E4O2-GD; Tue, 28 Feb 2023 19:19:17 +0000 Received: from mail-pl1-x62b.google.com ([2607:f8b0:4864:20::62b]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pX5VH-00E4M9-E2 for linux-riscv@lists.infradead.org; Tue, 28 Feb 2023 19:19:12 +0000 Received: by mail-pl1-x62b.google.com with SMTP id a2so1128635plm.4 for ; Tue, 28 Feb 2023 11:19:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1677611948; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=FpEVz7SmprPoPkB0vfE/PqJxuugSFBKj6AY2r5uLAhc=; b=oWlcXRzyqWqEIYwyzrAbhH5dfbtnZIzo1YdAD6EbxrkG1UYmywauWswlbWUb9RyzJT brrhvXg9BV/J80dlhPlO1Y21wLf6vRkFdXy7JICIvDrelyzHIZjZVwrR4yuaicL7f3Vk 2p3merJr6M4IafXoXz51BvBxgjw+2vFOvA7iQCX7+ipsnTqqyjWJ3THXEnrQ8p4gJgDk xZ3DYrEnn6dh5SSFWIpnSPW533U6fF1NRXuZZhGMXkF858tTyzkALowN2hKgVfeUNsrR 5wS/6VMndefgSb0UUhYGxgiYLa81lYWrHHI0iDazPBKk+F/PHzqrgvgcgWVcBnyOqxfC HgLQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1677611948; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=FpEVz7SmprPoPkB0vfE/PqJxuugSFBKj6AY2r5uLAhc=; b=nAPCVaRn1LfLtNUwDJ6jaqP8SCG7Ko3fFTM8HOOzDbCwDvcNYJAqK/SdA0dKewWuFT fvWx1ClGsr2pltIfFq3P8UcUSTzKfod8saeughNukzaVejBbxeJZsQ5m21I+rj8ppGbK /hMMZLVD8OHdnWkTmuxPtQ9RzP0ksHrWvEQ/HouHr2SMoEVfPEqEpSgRsCrolBVA7k/g USfqH5ANQg7rJ3Uv0Ey1gx98jmpt4HwFCbybOgJQc0SVEaoeG6MHkPHxjull45+z7z9P Vym8rbeCr7XZT8OTcriIvtvywh/GKKH8QBZBFOU8UTuplZnGBzPBv5nP1SbrNbhrI/jO Xodw== X-Gm-Message-State: AO0yUKUReitVhO21CtIS6bnOeKhxxLaytnyuTBOIWm5+n2CiEmc1JWtr eartRpNaWLCCkZcl4WDLxHM= X-Google-Smtp-Source: AK7set9nvpB6Jm7bh8EL2CSZ/onqaLVDtbrhvaG0Y49z4Hn9XsjcfvrcAyDG9rY99D0UL9m1Qq4bXA== X-Received: by 2002:a05:6a20:7f8e:b0:cb:6e9e:e6df with SMTP id d14-20020a056a207f8e00b000cb6e9ee6dfmr5180512pzj.14.1677611948146; Tue, 28 Feb 2023 11:19:08 -0800 (PST) Received: from ?IPV6:2001:df0:0:200c:112f:75e9:7ff2:6774? 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