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 8A253C3DA6D for ; Fri, 23 May 2025 05:31:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 256126B009D; Fri, 23 May 2025 01:31:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 207816B009F; Fri, 23 May 2025 01:31:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0CEEA6B00A0; Fri, 23 May 2025 01:31:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id D6C276B009D for ; Fri, 23 May 2025 01:31:45 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 8D279120D07 for ; Fri, 23 May 2025 05:31:45 +0000 (UTC) X-FDA: 83473050570.26.0C8F95A Received: from mail-pf1-f177.google.com (mail-pf1-f177.google.com [209.85.210.177]) by imf10.hostedemail.com (Postfix) with ESMTP id A114AC0004 for ; Fri, 23 May 2025 05:31:43 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=rivosinc-com.20230601.gappssmtp.com header.s=20230601 header.b=3G8ZtlPC; spf=pass (imf10.hostedemail.com: domain of debug@rivosinc.com designates 209.85.210.177 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=1747978303; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=DsODLDfRcPuDSErfbs+tzfaJx/MFrIF5cCrvvQql1Yk=; b=mO7yBPTswGoTNGkVRCjr4pBOdMoHRzMC+AJ1j+K464zyu+vr4+sE2XThnHeEBPXrV1A5sS eKQCbkDFAuPUrbdF8sUgWA0TQOcNE4AH525LxAEG1JznS6R+SulciDPRs7cM/U0LO0FBTD ecXFGabRoNcMfRxXDMiMd2ABDx5Wstk= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=rivosinc-com.20230601.gappssmtp.com header.s=20230601 header.b=3G8ZtlPC; spf=pass (imf10.hostedemail.com: domain of debug@rivosinc.com designates 209.85.210.177 as permitted sender) smtp.mailfrom=debug@rivosinc.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1747978303; a=rsa-sha256; cv=none; b=6Q00wXrA5D6KU7RovphZwn+LaaOeDIG5uLirRyWAPBiicIqF9p9+/R/FlmHaNN5kPIXQCn 5uBFa2HTpqmDxUrzoQ7IRvNv2tPFtcdG0oSc9sTsyXe0mrALh5EnJ1SAgECPjOT8Sr4dbu 7A4bHfzjKc7Gp0aKJI2byFxltkLvjvU= Received: by mail-pf1-f177.google.com with SMTP id d2e1a72fcca58-7370a2d1981so6608199b3a.2 for ; Thu, 22 May 2025 22:31:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rivosinc-com.20230601.gappssmtp.com; s=20230601; t=1747978302; x=1748583102; darn=kvack.org; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:from:to:cc:subject:date:message-id :reply-to; bh=DsODLDfRcPuDSErfbs+tzfaJx/MFrIF5cCrvvQql1Yk=; b=3G8ZtlPC8PODvYFsmgJDAP1EytKUjMv+Tyf/cWexGJLVmAdJzEPXOBQNxAaf1BAbSE aZ9BEh/cDljsChlMk+I7bqfT/MJoEc03Xb2FjzdTJ1JCoHYjXc/1MfwQ81E+BLL8g+io Kw2m+h/i6RXyN1cJ1YZOYrupeu4b7bRkESPylrSwGggbSw6t02/hu55etAFsHh2JOfZ1 r/XmL2UQNM3uqTqiRCCUOK6kgOTiAwsWr7vbtPYpmWJouNy1KbxHaqvKz6ne9kATkfvZ bP9bGERnvLdrDzSlp0ctzFpKGXVZDAKw0HA2sMHHVaAVM5XkdrTl3ro0CoBiVCT5dnb2 sOHQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747978302; x=1748583102; h=cc:to:in-reply-to:references:message-id:content-transfer-encoding :mime-version:subject:date:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=DsODLDfRcPuDSErfbs+tzfaJx/MFrIF5cCrvvQql1Yk=; b=EnEH2G1BuSXUvjkvgmNltmbyGU3sCcevlN8mtxFVsjyIsVLDZCyvMagmTJQlXBnTG7 fCreAFIWW8YN1jRqfVzOSyZsQg8vYkOf+Yd5/sLDRgwN6FoPgqAvHsKBEB3+YAybsx7p Ebx3Iz1hX6GRCKzl8AxB7bmLMHfF5ewQBUdeIQkZRgLzfAzO/K9Rm1s7Y8RTetha1YYn qZ9eIo7+xbYOxbn5d90D+qNW7LOySnLwtsdmP4yI8tjVS2LDjj1h6gXSuOjfclspruXx LhDHI6qIOqFeOfGZ0figcwuuaqPj0HzUo/c1etrLU2n1ww39ps9UqRYo635PzfWp+85I DwUg== X-Forwarded-Encrypted: i=1; AJvYcCWpBa7MfgOKVc0KocCt/1KvUbBRCBckUl1lAMEElV9gy2tPtEV0RLSdSj/TwTzAmzjLNim9QDwfpg==@kvack.org X-Gm-Message-State: AOJu0YwON0KE8ek1lt41HS/93TulWAT5B/+F2PgNdN+jcagYoEktOc9t QAp0FTzUn31oIXQ8lJPG3TBxzeJFnrNpfUD2WCX8OAY98GfPPx/0OvlcRhyCKPBfJ0I= X-Gm-Gg: ASbGncs/4F0PN3tYRkzrd0ekR3n55rips0uygCPX7BIjLGSmqvmVnxsyRY7pe5fibEk GXCJiJKQqmi/cTesdjJbZ7a5tZ0wT0WX3iaN81XA4QhZRj/h+L1n5xiH+fAOiOXswd8EUgnuLlB avZJ19ElKOkQTRk3v/fgP1Hx3sGMK5JhrJ4nckHPkxx43/wOk5o7SGN1Ctvl3hvguzpxJUf0ILc /9plL8Gv2/awebD9d5IWYQ6P1t1jx70gjqNeP1m+yrE2WeVE3axuh1g2fjZSpfJD0x7nhs+8Ky4 iTjc/NTFGIB5ImZ/3U34W91dzGI1bhwqL8zEcaAzafpbr9nc93bvmGThMRgApg== X-Google-Smtp-Source: AGHT+IGDLVr6ZJ9g2UKmuR3DGUz8wUaNVCkk9XGn0el3OWW6yYG/d5yInq98aQU+8QHvwqvNBOnbXw== X-Received: by 2002:a05:6a00:399e:b0:736:50d1:fc84 with SMTP id d2e1a72fcca58-742acd726demr38701066b3a.21.1747978302507; Thu, 22 May 2025 22:31:42 -0700 (PDT) Received: from debug.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-742a982a0a4sm12474336b3a.101.2025.05.22.22.31.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 May 2025 22:31:42 -0700 (PDT) From: Deepak Gupta Date: Thu, 22 May 2025 22:31:12 -0700 Subject: [PATCH v16 09/27] riscv mmu: write protect and shadow stack MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250522-v5_user_cfi_series-v16-9-64f61a35eee7@rivosinc.com> References: <20250522-v5_user_cfi_series-v16-0-64f61a35eee7@rivosinc.com> In-Reply-To: <20250522-v5_user_cfi_series-v16-0-64f61a35eee7@rivosinc.com> To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , Jann Horn , Conor Dooley , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com, rust-for-linux@vger.kernel.org, Zong Li , Deepak Gupta X-Mailer: b4 0.13.0 X-Rspam-User: X-Rspamd-Queue-Id: A114AC0004 X-Rspamd-Server: rspam09 X-Stat-Signature: k85wa3hdsp6p88ffqdqrrxa4bayzhi9r X-HE-Tag: 1747978303-487026 X-HE-Meta: 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 XpEqywhM 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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: `fork` implements copy on write (COW) by making pages readonly in child and parent both. ptep_set_wrprotect and pte_wrprotect clears _PAGE_WRITE in PTE. Assumption is that page is readable and on fault copy on write happens. To implement COW on shadow stack pages, clearing up W bit makes them XWR = 000. This will result in wrong PTE setting which says no perms but V=1 and PFN field pointing to final page. Instead desired behavior is to turn it into a readable page, take an access (load/store) fault on sspush/sspop (shadow stack) and then perform COW on such pages. This way regular reads would still be allowed and not lead to COW maintaining current behavior of COW on non-shadow stack but writeable memory. On the other hand it doesn't interfere with existing COW for read-write memory. Assumption is always that _PAGE_READ must have been set and thus setting _PAGE_READ is harmless. Reviewed-by: Alexandre Ghiti Reviewed-by: Zong Li Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/pgtable.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 60d4821627d2..4e3431ccf634 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -423,7 +423,7 @@ static inline int pte_devmap(pte_t pte) static inline pte_t pte_wrprotect(pte_t pte) { - return __pte(pte_val(pte) & ~(_PAGE_WRITE)); + return __pte((pte_val(pte) & ~(_PAGE_WRITE)) | (_PAGE_READ)); } /* static inline pte_t pte_mkread(pte_t pte) */ @@ -624,7 +624,15 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long address, pte_t *ptep) { - atomic_long_and(~(unsigned long)_PAGE_WRITE, (atomic_long_t *)ptep); + pte_t read_pte = READ_ONCE(*ptep); + /* + * ptep_set_wrprotect can be called for shadow stack ranges too. + * shadow stack memory is XWR = 010 and thus clearing _PAGE_WRITE will lead to + * encoding 000b which is wrong encoding with V = 1. This should lead to page fault + * but we dont want this wrong configuration to be set in page tables. + */ + atomic_long_set((atomic_long_t *)ptep, + ((pte_val(read_pte) & ~(unsigned long)_PAGE_WRITE) | _PAGE_READ)); } #define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH -- 2.43.0