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[23.128.96.18]) by mx.google.com with ESMTP id ka11si10216818ejc.367.2021.06.13.12.53.42; Sun, 13 Jun 2021 12:54:04 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231853AbhFMTxE (ORCPT + 99 others); Sun, 13 Jun 2021 15:53:04 -0400 Received: from mail-out.m-online.net ([212.18.0.9]:56880 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231788AbhFMTxE (ORCPT ); Sun, 13 Jun 2021 15:53:04 -0400 Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 4G34vN64Cwz1qtQV; Sun, 13 Jun 2021 21:50:56 +0200 (CEST) Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 4G34vN363qz1qsYj; Sun, 13 Jun 2021 21:50:56 +0200 (CEST) X-Virus-Scanned: amavisd-new at mnet-online.de Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.70]) (amavisd-new, port 10024) with ESMTP id HJAVNxtJklRu; Sun, 13 Jun 2021 21:50:54 +0200 (CEST) X-Auth-Info: LElrgumow5j7MizGUQKNpWrnXWIF9Qr7mZEEQCIJzLKJl+b0lrS27gPvl8MTWt4G Received: from igel.home (ppp-46-244-177-185.dynamic.mnet-online.de [46.244.177.185]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.mnet-online.de (Postfix) with ESMTPSA; Sun, 13 Jun 2021 21:50:54 +0200 (CEST) Received: by igel.home (Postfix, from userid 1000) id D34602C369D; Sun, 13 Jun 2021 21:50:53 +0200 (CEST) From: Andreas Schwab To: Jisheng Zhang Cc: Paul Walmsley , Palmer Dabbelt , Albert Ou , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Luke Nelson , Xi Wang , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, netdev@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH 7/9] riscv: bpf: Avoid breaking W^X References: <20210330022144.150edc6e@xhacker> <20210330022521.2a904a8c@xhacker> <87o8ccqypw.fsf@igel.home> <20210612002334.6af72545@xhacker> <87bl8cqrpv.fsf@igel.home> <20210614010546.7a0d5584@xhacker> X-Yow: .. Once upon a time, four AMPHIBIOUS HOG CALLERS attacked a family of DEFENSELESS, SENSITIVE COIN COLLECTORS and brought DOWN their PROPERTY VALUES!! Date: Sun, 13 Jun 2021 21:50:53 +0200 In-Reply-To: <20210614010546.7a0d5584@xhacker> (Jisheng Zhang's message of "Mon, 14 Jun 2021 01:05:46 +0800") Message-ID: <87im2hsfvm.fsf@igel.home> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Jun 14 2021, Jisheng Zhang wrote: > I think I found the root cause: commit 2bfc6cd81bd ("move kernel mapping > outside of linear mapping") moves BPF JIT region after the kernel: > > #define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end) > > The &_end is unlikely aligned with PMD SIZE, so the front bpf jit region > sits with kernel .data section in one PMD. But kenrel is mapped in PMD SIZE, > so when bpf_jit_binary_lock_ro() is called to make the first bpf jit prog > ROX, we will make part of kernel .data section RO too, so when we write, for example > memset the .data section, MMU will trigger store page fault. > > To fix the issue, we need to make the bpf jit region PMD size aligned by either > patch BPF_JIT_REGION_START to align on PMD size rather than PAGE SIZE, or > something as below patch to move the BPF region before modules region: > > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h > index 9469f464e71a..997b894edbc2 100644 > --- a/arch/riscv/include/asm/pgtable.h > +++ b/arch/riscv/include/asm/pgtable.h > @@ -31,8 +31,8 @@ > #define BPF_JIT_REGION_SIZE (SZ_128M) > #ifdef CONFIG_64BIT > /* KASLR should leave at least 128MB for BPF after the kernel */ > -#define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end) > -#define BPF_JIT_REGION_END (BPF_JIT_REGION_START + BPF_JIT_REGION_SIZE) > +#define BPF_JIT_REGION_START (BPF_JIT_REGION_END - BPF_JIT_REGION_SIZE) > +#define BPF_JIT_REGION_END (MODULES_VADDR) > #else > #define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE) > #define BPF_JIT_REGION_END (VMALLOC_END) > @@ -40,8 +40,8 @@ > > /* Modules always live before the kernel */ > #ifdef CONFIG_64BIT > -#define MODULES_VADDR (PFN_ALIGN((unsigned long)&_end) - SZ_2G) > #define MODULES_END (PFN_ALIGN((unsigned long)&_start)) > +#define MODULES_VADDR (MODULES_END - SZ_128M) > #endif > > > can you please try it? Per my test, the issue is fixed. I can confirm that this fixes the issue. Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different."