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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 109ACC48BE5 for ; Tue, 15 Jun 2021 12:30:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E4E1461420 for ; Tue, 15 Jun 2021 12:30:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230152AbhFOMcO (ORCPT ); Tue, 15 Jun 2021 08:32:14 -0400 Received: from www62.your-server.de ([213.133.104.62]:53820 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229989AbhFOMcM (ORCPT ); Tue, 15 Jun 2021 08:32:12 -0400 Received: from sslproxy02.your-server.de ([78.47.166.47]) by www62.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92.3) (envelope-from ) id 1lt8CZ-000G4r-Ko; Tue, 15 Jun 2021 14:29:55 +0200 Received: from [85.7.101.30] (helo=linux-3.home) by sslproxy02.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lt8CZ-0005iV-78; Tue, 15 Jun 2021 14:29:55 +0200 Subject: Re: [PATCH] riscv: Ensure BPF_JIT_REGION_START aligned with PMD size To: Jisheng Zhang , Andreas Schwab , Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Alexei Starovoitov , 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 References: <20210330022144.150edc6e@xhacker> <20210330022521.2a904a8c@xhacker> <87o8ccqypw.fsf@igel.home> <20210612002334.6af72545@xhacker> <87bl8cqrpv.fsf@igel.home> <20210614010546.7a0d5584@xhacker> <87im2hsfvm.fsf@igel.home> <20210615004928.2d27d2ac@xhacker> From: Daniel Borkmann Message-ID: <3c7ec52d-7fa3-dfac-239c-989ea1cc37ee@iogearbox.net> Date: Tue, 15 Jun 2021 14:29:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20210615004928.2d27d2ac@xhacker> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.103.2/26202/Tue Jun 15 13:21:24 2021) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 6/14/21 6:49 PM, Jisheng Zhang wrote: > From: Jisheng Zhang > > Andreas reported commit fc8504765ec5 ("riscv: bpf: Avoid breaking W^X") > breaks booting with one kind of config file, I reproduced a kernel panic > with the config: > > [ 0.138553] Unable to handle kernel paging request at virtual address ffffffff81201220 > [ 0.139159] Oops [#1] > [ 0.139303] Modules linked in: > [ 0.139601] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc5-default+ #1 > [ 0.139934] Hardware name: riscv-virtio,qemu (DT) > [ 0.140193] epc : __memset+0xc4/0xfc > [ 0.140416] ra : skb_flow_dissector_init+0x1e/0x82 > [ 0.140609] epc : ffffffff8029806c ra : ffffffff8033be78 sp : ffffffe001647da0 > [ 0.140878] gp : ffffffff81134b08 tp : ffffffe001654380 t0 : ffffffff81201158 > [ 0.141156] t1 : 0000000000000002 t2 : 0000000000000154 s0 : ffffffe001647dd0 > [ 0.141424] s1 : ffffffff80a43250 a0 : ffffffff81201220 a1 : 0000000000000000 > [ 0.141654] a2 : 000000000000003c a3 : ffffffff81201258 a4 : 0000000000000064 > [ 0.141893] a5 : ffffffff8029806c a6 : 0000000000000040 a7 : ffffffffffffffff > [ 0.142126] s2 : ffffffff81201220 s3 : 0000000000000009 s4 : ffffffff81135088 > [ 0.142353] s5 : ffffffff81135038 s6 : ffffffff8080ce80 s7 : ffffffff80800438 > [ 0.142584] s8 : ffffffff80bc6578 s9 : 0000000000000008 s10: ffffffff806000ac > [ 0.142810] s11: 0000000000000000 t3 : fffffffffffffffc t4 : 0000000000000000 > [ 0.143042] t5 : 0000000000000155 t6 : 00000000000003ff > [ 0.143220] status: 0000000000000120 badaddr: ffffffff81201220 cause: 000000000000000f > [ 0.143560] [] __memset+0xc4/0xfc > [ 0.143859] [] init_default_flow_dissectors+0x22/0x60 > [ 0.144092] [] do_one_initcall+0x3e/0x168 > [ 0.144278] [] kernel_init_freeable+0x1c8/0x224 > [ 0.144479] [] kernel_init+0x12/0x110 > [ 0.144658] [] ret_from_exception+0x0/0xc > [ 0.145124] ---[ end trace f1e9643daa46d591 ]--- > > After some investigation, I think I found the root cause: commit > 2bfc6cd81bd ("move kernel mapping outside of linear mapping") moves > BPF JIT region after the kernel: > > The &_end is unlikely aligned with PMD size, so the front bpf jit > region sits with part of kernel .data section in one PMD size mapping. > But kernel is mapped in PMD SIZE, 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 to, for example memset the > .data section, MMU will trigger a store page fault. > > To fix the issue, we need to ensure the BPF JIT region is PMD size > aligned. This patch acchieve this goal by restoring the BPF JIT region > to original position, I.E the 128MB before kernel .text section. > > Reported-by: Andreas Schwab > Signed-off-by: Jisheng Zhang > --- > arch/riscv/include/asm/pgtable.h | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h > index 9469f464e71a..380cd3a7e548 100644 > --- a/arch/riscv/include/asm/pgtable.h > +++ b/arch/riscv/include/asm/pgtable.h > @@ -30,9 +30,8 @@ > > #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_END) > #else > #define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE) > #define BPF_JIT_REGION_END (VMALLOC_END) I presume this fix will be routed via riscv tree? Thanks, Daniel