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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9EABC25B10 for ; Mon, 13 May 2024 18:41:43 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0D2546B02C8; Mon, 13 May 2024 14:41:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 05AF66B02C9; Mon, 13 May 2024 14:41:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E16A36B02CA; Mon, 13 May 2024 14:41:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id BF9426B02C8 for ; Mon, 13 May 2024 14:41:42 -0400 (EDT) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 28243A0C22 for ; Mon, 13 May 2024 18:41:42 +0000 (UTC) X-FDA: 82114241244.22.E17F875 Received: from mail-pf1-f178.google.com (mail-pf1-f178.google.com [209.85.210.178]) by imf15.hostedemail.com (Postfix) with ESMTP id 44A9BA0019 for ; Mon, 13 May 2024 18:41:40 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=rivosinc-com.20230601.gappssmtp.com header.s=20230601 header.b=ZXn6mcZj; spf=pass (imf15.hostedemail.com: domain of debug@rivosinc.com designates 209.85.210.178 as permitted sender) smtp.mailfrom=debug@rivosinc.com; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1715625700; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=XY9wUjNICjiX4OH8fN35kly5zcKWL5OlXrAU/KY+MCs=; b=JWy57k6E1MITvAKTHFRLX8oIi133yn72WzIceOEN1Z2HEbKSoNuyKzEqyJthx2LI1x1hm+ fD91heW62zQkkm/lIMx8VjCJl8nNHf0gMTaCGnB5OLw2MEKqo0FAf1PNwB8HeT+ToBkvD4 Q4Ug01zgIniV8eS54sI2ukRlicdieaI= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=rivosinc-com.20230601.gappssmtp.com header.s=20230601 header.b=ZXn6mcZj; spf=pass (imf15.hostedemail.com: domain of debug@rivosinc.com designates 209.85.210.178 as permitted sender) smtp.mailfrom=debug@rivosinc.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1715625700; a=rsa-sha256; cv=none; b=crk93Qvh0UXL3jzZTEZSRNomzU67yP3abqqLEGsFg/NrD/KGjiC3Pbit3rlB3y7eg+A8yT nBQb6CHTHP4pr1HiLrqpOVCCkTl22YUKyuqdKKjDC3D6ey3tpueYeR+B+0zXQlD58e9bY6 5Ja4ScqsJwRH2X2G30f3gmtJ42VRBi8= Received: by mail-pf1-f178.google.com with SMTP id d2e1a72fcca58-6f4603237e0so3242846b3a.0 for ; Mon, 13 May 2024 11:41:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1715625699; x=1716230499; darn=kvack.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=XY9wUjNICjiX4OH8fN35kly5zcKWL5OlXrAU/KY+MCs=; b=ZXn6mcZjWJDEiDStEpGkRJAIXZRhgjcSDmbqHCh4AmNnyCLyOY1tj8v4kKvAzsThjQ LnfG4+ptoX5CR8uOVZZA9gMSr31qHENmEkLKaJdYsfMKh9EflnIE3iNwVEVLw9WpptVp fbyLcxbTx+f8VGwQBUPbEaYRhL7xasTFLh7fnq79ffKIXlLiSxAubBhZgJJRnE918iK8 hrIDPsU5Z2YV0ySKwEEd1Vmy8+MrvTQgAprJvShpVIf17COc60h/mnXN2pmQBuW4lPM1 5MRJw3t2J7qJDrB19GtYiBzFwf0NzHySSIhIFKHXGOa8rq2fhK7t2HXOE/HjW80YZkZm yNjw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1715625699; x=1716230499; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=XY9wUjNICjiX4OH8fN35kly5zcKWL5OlXrAU/KY+MCs=; b=j77Q1GnHTCAz2fIQ9TFvUlo1+Z2zwjbyTL+snPP/fBclWUTvHwmRS52Xb4NvrpqAj6 +CAM3Ty6bn1oo3wrWlzRnNh8iOpbqik3XuKM6znrtGi8wjcwnASU2wTy9v9X2Rj5b6hE y0Fh09tgywmNX9aMR7K5Bux7X5QlPi0BzwvjzN5sz6uc8+pN1ZhCFEujynLKndGUzGPb vvoNjAScrjsZBS/L6IM5WLsaXQ3qkpcA+dqqAwj/r51XEuhw6xtxm6P+oMx8iwAIBLp+ h1uKlV6gIPDNm/eEnKfgVZADWLPgZQHq3ZaOKnvbGxNtFphk0mCLMrms3NfPy/gZtBZw zUTg== X-Forwarded-Encrypted: i=1; AJvYcCU8Ms2bzLcUwYWYJfSyvyTlFF+QOuzaq+tYIyrZDjB0+WSMk4PwRDG16eWa4jeWS061KAHqwId6/IwPBF884B2WNiw= X-Gm-Message-State: AOJu0YwwHAqsoD/lR2g1rvAD2E1oSjqa9hEBxQ7+XvvJuhMfpc83YdqZ vHHj7m1LhT/eGPJ7vYIPGL6PJYtxxAKnjGV9upKKztw21DVf55pFrGXBksTKW/I= X-Google-Smtp-Source: AGHT+IFDpGJAozuUAoSCJToHHLthoDO4Bo/1R8ix+nOMfz5BRfFaIeih/L/fVxquTOUi37YhZTLrFg== X-Received: by 2002:a05:6a00:198a:b0:6f4:4b84:7c17 with SMTP id d2e1a72fcca58-6f4c9338971mr19674022b3a.13.1715625698960; Mon, 13 May 2024 11:41:38 -0700 (PDT) Received: from debug.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-6f4d2b2f9eesm7681513b3a.212.2024.05.13.11.41.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 May 2024 11:41:38 -0700 (PDT) Date: Mon, 13 May 2024 11:41:34 -0700 From: Deepak Gupta To: Charlie Jenkins Cc: paul.walmsley@sifive.com, rick.p.edgecombe@intel.com, broonie@kernel.org, Szabolcs.Nagy@arm.com, kito.cheng@sifive.com, keescook@chromium.org, ajones@ventanamicro.com, conor.dooley@microchip.com, cleger@rivosinc.com, atishp@atishpatra.org, alex@ghiti.fr, bjorn@rivosinc.com, alexghiti@rivosinc.com, samuel.holland@sifive.com, conor@kernel.org, linux-doc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kselftest@vger.kernel.org, corbet@lwn.net, palmer@dabbelt.com, aou@eecs.berkeley.edu, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, oleg@redhat.com, akpm@linux-foundation.org, arnd@arndb.de, ebiederm@xmission.com, Liam.Howlett@oracle.com, vbabka@suse.cz, lstoakes@gmail.com, shuah@kernel.org, brauner@kernel.org, andy.chiu@sifive.com, jerry.shih@sifive.com, hankuan.chen@sifive.com, greentime.hu@sifive.com, evan@rivosinc.com, xiao.w.wang@intel.com, apatel@ventanamicro.com, mchitale@ventanamicro.com, dbarboza@ventanamicro.com, sameo@rivosinc.com, shikemeng@huaweicloud.com, willy@infradead.org, vincent.chen@sifive.com, guoren@kernel.org, samitolvanen@google.com, songshuaishuai@tinylab.org, gerg@kernel.org, heiko@sntech.de, bhe@redhat.com, jeeheng.sia@starfivetech.com, cyy@cyyself.name, maskray@google.com, ancientmodern4@gmail.com, mathis.salmen@matsal.de, cuiyunhui@bytedance.com, bgray@linux.ibm.com, mpe@ellerman.id.au, baruch@tkos.co.il, alx@kernel.org, david@redhat.com, catalin.marinas@arm.com, revest@chromium.org, josh@joshtriplett.org, shr@devkernel.io, deller@gmx.de, omosnace@redhat.com, ojeda@kernel.org, jhubbard@nvidia.com Subject: Re: [PATCH v3 10/29] riscv/mm : ensure PROT_WRITE leads to VM_READ | VM_WRITE Message-ID: References: <20240403234054.2020347-1-debug@rivosinc.com> <20240403234054.2020347-11-debug@rivosinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 44A9BA0019 X-Stat-Signature: ko9tqh4t37yf7k8dipi7suw4wjmx5hnn X-HE-Tag: 1715625700-850942 X-HE-Meta: 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 urXB+SpC 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 13, 2024 at 11:36:49AM -0700, Charlie Jenkins wrote: >On Mon, May 13, 2024 at 10:47:25AM -0700, Deepak Gupta wrote: >> On Fri, May 10, 2024 at 02:02:54PM -0700, Charlie Jenkins wrote: >> > On Wed, Apr 03, 2024 at 04:34:58PM -0700, Deepak Gupta wrote: >> > > `arch_calc_vm_prot_bits` is implemented on risc-v to return VM_READ | >> > > VM_WRITE if PROT_WRITE is specified. Similarly `riscv_sys_mmap` is >> > > updated to convert all incoming PROT_WRITE to (PROT_WRITE | PROT_READ). >> > > This is to make sure that any existing apps using PROT_WRITE still work. >> > > >> > > Earlier `protection_map[VM_WRITE]` used to pick read-write PTE encodings. >> > > Now `protection_map[VM_WRITE]` will always pick PAGE_SHADOWSTACK PTE >> > > encodings for shadow stack. Above changes ensure that existing apps >> > > continue to work because underneath kernel will be picking >> > > `protection_map[VM_WRITE|VM_READ]` PTE encodings. >> > > >> > > Signed-off-by: Deepak Gupta >> > > --- >> > > arch/riscv/include/asm/mman.h | 24 ++++++++++++++++++++++++ >> > > arch/riscv/include/asm/pgtable.h | 1 + >> > > arch/riscv/kernel/sys_riscv.c | 11 +++++++++++ >> > > arch/riscv/mm/init.c | 2 +- >> > > mm/mmap.c | 1 + >> > > 5 files changed, 38 insertions(+), 1 deletion(-) >> > > create mode 100644 arch/riscv/include/asm/mman.h >> > > >> > > diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h >> > > new file mode 100644 >> > > index 000000000000..ef9fedf32546 >> > > --- /dev/null >> > > +++ b/arch/riscv/include/asm/mman.h >> > > @@ -0,0 +1,24 @@ >> > > +/* SPDX-License-Identifier: GPL-2.0 */ >> > > +#ifndef __ASM_MMAN_H__ >> > > +#define __ASM_MMAN_H__ >> > > + >> > > +#include >> > > +#include >> > > +#include >> > > + >> > > +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, >> > > + unsigned long pkey __always_unused) >> > > +{ >> > > + unsigned long ret = 0; >> > > + >> > > + /* >> > > + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. >> > > + * Only VM_WRITE means shadow stack. >> > > + */ >> > > + if (prot & PROT_WRITE) >> > > + ret = (VM_READ | VM_WRITE); >> > > + return ret; >> > > +} >> > > +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) >> > > + >> > > +#endif /* ! __ASM_MMAN_H__ */ >> > > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h >> > > index 6066822e7396..4d5983bc6766 100644 >> > > --- a/arch/riscv/include/asm/pgtable.h >> > > +++ b/arch/riscv/include/asm/pgtable.h >> > > @@ -184,6 +184,7 @@ extern struct pt_alloc_ops pt_ops __initdata; >> > > #define PAGE_READ_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_EXEC) >> > > #define PAGE_WRITE_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | \ >> > > _PAGE_EXEC | _PAGE_WRITE) >> > > +#define PAGE_SHADOWSTACK __pgprot(_PAGE_BASE | _PAGE_WRITE) >> > > >> > > #define PAGE_COPY PAGE_READ >> > > #define PAGE_COPY_EXEC PAGE_READ_EXEC >> > > diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c >> > > index f1c1416a9f1e..846c36b1b3d5 100644 >> > > --- a/arch/riscv/kernel/sys_riscv.c >> > > +++ b/arch/riscv/kernel/sys_riscv.c >> > > @@ -8,6 +8,8 @@ >> > > #include >> > > #include >> > > #include >> > > +#include >> > > +#include >> > > >> > > static long riscv_sys_mmap(unsigned long addr, unsigned long len, >> > > unsigned long prot, unsigned long flags, >> > > @@ -17,6 +19,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, >> > > if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) >> > > return -EINVAL; >> > > >> > > + /* >> > > + * If only PROT_WRITE is specified then extend that to PROT_READ >> > > + * protection_map[VM_WRITE] is now going to select shadow stack encodings. >> > > + * So specifying PROT_WRITE actually should select protection_map [VM_WRITE | VM_READ] >> > > + * If user wants to create shadow stack then they should use `map_shadow_stack` syscall. >> > > + */ >> > > + if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) >> > >> > The comments says that this should extend to PROT_READ if only >> > PROT_WRITE is specified. This condition instead is checking if >> > PROT_WRITE is selected but PROT_READ is not. If prot is (VM_EXEC | >> > VM_WRITE) then it would be extended to (VM_EXEC | VM_WRITE | VM_READ). >> > This will not currently cause any issues because these both map to the >> > same value in the protection_map PAGE_COPY_EXEC, however this seems to >> > be not the intention of this change. >> > >> > prot == PROT_WRITE better suits the condition explained in the comment. >> >> If someone specifies this (PROT_EXEC | PROT_WRITE) today, it works because >> of the way permissions are setup in `protection_map`. On risc-v there is no >> way to have a page which is execute and write only. So expectation is that >> if some apps were using `PROT_EXEC | PROT_WRITE` today, they were working >> because internally it was translating to read, write and execute on page >> permissions level. This patch make sure that, it stays same from page >> permissions perspective. >> >> If someone was using PROT_EXEC, it may translate to execute only and this change >> doesn't impact that. >> >> Patch simply looks for presence of `PROT_WRITE` and absence of `PROT_READ` in >> protection flags and if that condition is satisfied, it assumes that caller assumed >> page is going to be read allowed as well. > >The purpose of this change is for compatibility with shadow stack pages >but this affects flags for pages that are not shadow stack pages. >Adding PROT_READ to the other cases is redundant as protection_map >already handles that mapping. Permissions being strictly PROT_WRITE is >the only case that needs to be handled, and is the only case that is >called out in the commit message and in the comment. Yeah that's fine. I can change the commit message or just strictly check for PROT_WRITE. It doesn't change bottomline, I am fine with either option. Let me know your preference. > >- Charlie > >> >> >> > >> > > + prot |= PROT_READ; >> > > + >> > > return ksys_mmap_pgoff(addr, len, prot, flags, fd, >> > > offset >> (PAGE_SHIFT - page_shift_offset)); >> > > } >> > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >> > > index fa34cf55037b..98e5ece4052a 100644 >> > > --- a/arch/riscv/mm/init.c >> > > +++ b/arch/riscv/mm/init.c >> > > @@ -299,7 +299,7 @@ pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); >> > > static const pgprot_t protection_map[16] = { >> > > [VM_NONE] = PAGE_NONE, >> > > [VM_READ] = PAGE_READ, >> > > - [VM_WRITE] = PAGE_COPY, >> > > + [VM_WRITE] = PAGE_SHADOWSTACK, >> > > [VM_WRITE | VM_READ] = PAGE_COPY, >> > > [VM_EXEC] = PAGE_EXEC, >> > > [VM_EXEC | VM_READ] = PAGE_READ_EXEC, >> > > diff --git a/mm/mmap.c b/mm/mmap.c >> > > index d89770eaab6b..57a974f49b00 100644 >> > > --- a/mm/mmap.c >> > > +++ b/mm/mmap.c >> > > @@ -47,6 +47,7 @@ >> > > #include >> > > #include >> > > #include >> > > +#include >> > >> > It doesn't seem like this is necessary for this patch. >> >> Thanks. Yeah it looks like I forgot to remove this over the churn. >> Will fix it. >> >> > >> > - Charlie >> > >> > > >> > > #include >> > > #include >> > > -- >> > > 2.43.2 >> > >