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=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 A18EDC433ED for ; Mon, 26 Apr 2021 06:52:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id F172A61249 for ; Mon, 26 Apr 2021 06:52:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F172A61249 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=shutemov.name Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 2824C6B006C; Mon, 26 Apr 2021 02:52:43 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 232D56B006E; Mon, 26 Apr 2021 02:52:43 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 036EF6B0070; Mon, 26 Apr 2021 02:52:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0119.hostedemail.com [216.40.44.119]) by kanga.kvack.org (Postfix) with ESMTP id D1B346B006C for ; Mon, 26 Apr 2021 02:52:42 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 880D018037FCF for ; Mon, 26 Apr 2021 06:52:42 +0000 (UTC) X-FDA: 78073600164.08.DEA3E41 Received: from mail-lf1-f51.google.com (mail-lf1-f51.google.com [209.85.167.51]) by imf05.hostedemail.com (Postfix) with ESMTP id 923B5E00010B for ; Mon, 26 Apr 2021 06:52:40 +0000 (UTC) Received: by mail-lf1-f51.google.com with SMTP id j4so47168488lfp.0 for ; Sun, 25 Apr 2021 23:52:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=vSMB9b06mxY/vpzupY2c4eRnFMLlF0PHvUHRcvumkgg=; b=UTW/TxvcFWW0wd0jUtmc5bZHz+RBqjHyTKfhjGUfNJ0gMZGF5u/r39dSd0sCnXiM0F mWUx3Bo5Wox/miXa7Y+8FPKV4FlUkLgJbx7sC8A35/ULd2MMQ5HC7zZbqQCHjBRxLW/U JKAB2yloQb7jDw3yMLK9Vm6Q2Ol+VqIDTXSzzp5gJx5/JCDaRhZsv3V8po/CE0o0gRoA 3rMRrMkGVPKPzAT3EgSKbTOlxehU6MaG86dYf8aNvHscerYlCcRKrzhmQoYZjtypHyrH DMSnK6hBwONDGCMzBS7cjZL5iZnrmcT7mLNALBKyM6BaaQi14YNuJxL+v0KOMSlUMNTd zr8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=vSMB9b06mxY/vpzupY2c4eRnFMLlF0PHvUHRcvumkgg=; b=MDp+Ieqvckgv9xisHsXm3FHOiR/eBFuWaUTYt3FJxHNOWQVheoqBJGijpev9TPGseZ SieroYe0oTQy7AGc6J5ne2sRjR3fhx4tgU03IMFzhEmI4EFxLy0LS41+4yzb1rJF2iKn eOdPUDJkpDSoxrqM/y/m0sqf46bkutEAoWqwTvCpw/Lxo+GvpWIZUjrqEcOSieerETRf fO9+d/pa/wjpSYOazfJmoKY+iTReICzs4FU852Iv3dYByDFYzlbaMxdf+yC3u6PW3SSs 3EtDA67/00/0nr/oJZ1ygzewbvVTpZ/75ZqGeyJ8EFpErZk7RkhrNEMc9Wd8zHk+/zqJ rMtA== X-Gm-Message-State: AOAM531TSrvZMoWJ/uLjlxgJrzn8Kv/QLmThL+Rb/QTDjUhxkK2rd/G4 9iJ22YaJOy9zrQ0c1U9S3vtD8w== X-Google-Smtp-Source: ABdhPJw+9dvYBRmAGSJb4PMciQ6ryoUSVfD6TH4Et3dNdEWA5/MZDD+GpUEvmSX2bX+W85Wbs42Nfg== X-Received: by 2002:ac2:5f1b:: with SMTP id 27mr11685539lfq.425.1619419960641; Sun, 25 Apr 2021 23:52:40 -0700 (PDT) Received: from box.localdomain ([86.57.175.117]) by smtp.gmail.com with ESMTPSA id v3sm285203lfo.257.2021.04.25.23.52.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 25 Apr 2021 23:52:39 -0700 (PDT) Received: by box.localdomain (Postfix, from userid 1000) id 973ED1026AB; Mon, 26 Apr 2021 09:52:43 +0300 (+03) Date: Mon, 26 Apr 2021 09:52:43 +0300 From: "Kirill A. Shutemov" To: Yu-cheng Yu Cc: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang , Pengfei Xu , Haitao Huang , "Kirill A . Shutemov" Subject: Re: [PATCH v25 30/30] mm: Introduce PROT_SHSTK for shadow stack Message-ID: <20210426065243.ozh6doz6q5xonrqe@box.shutemov.name> References: <20210415221419.31835-1-yu-cheng.yu@intel.com> <20210415221419.31835-31-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210415221419.31835-31-yu-cheng.yu@intel.com> X-Rspamd-Queue-Id: 923B5E00010B X-Stat-Signature: uftizyxb1yreq35gs88i1kofgeezeit7 X-Rspamd-Server: rspam02 Received-SPF: none (shutemov.name>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=mail-lf1-f51.google.com; client-ip=209.85.167.51 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1619419960-648206 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: On Thu, Apr 15, 2021 at 03:14:19PM -0700, Yu-cheng Yu wrote: > There are three possible options to create a shadow stack allocation API: > an arch_prctl, a new syscall, or adding PROT_SHSTK to mmap()/mprotect(). > Each has its advantages and compromises. > > An arch_prctl() is the least intrusive. However, the existing x86 > arch_prctl() takes only two parameters. Multiple parameters must be > passed in a memory buffer. There is a proposal to pass more parameters in > registers [1], but no active discussion on that. > > A new syscall minimizes compatibility issues and offers an extensible frame > work to other architectures, but this will likely result in some overlap of > mmap()/mprotect(). > > The introduction of PROT_SHSTK to mmap()/mprotect() takes advantage of Maybe PROT_SHADOW_STACK? > existing APIs. The x86-specific PROT_SHSTK is translated to > VM_SHADOW_STACK and a shadow stack mapping is created without reinventing > the wheel. There are potential pitfalls though. The most obvious one > would be using this as a bypass to shadow stack protection. However, the > attacker would have to get to the syscall first. > > [1] https://lore.kernel.org/lkml/20200828121624.108243-1-hjl.tools@gmail.com/ > > Signed-off-by: Yu-cheng Yu > Cc: Kees Cook > Cc: Kirill A. Shutemov > --- > v24: > - Update arch_calc_vm_prot_bits(), leave PROT* checking to > arch_validate_prot(). > - Update arch_validate_prot(), leave vma flags checking to > arch_validate_flags(). > - Add arch_validate_flags(). > > arch/x86/include/asm/mman.h | 59 +++++++++++++++++++++++++++++++- > arch/x86/include/uapi/asm/mman.h | 1 + > include/linux/mm.h | 1 + > 3 files changed, 60 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/include/asm/mman.h b/arch/x86/include/asm/mman.h > index 629f6c81263a..1821c179f35d 100644 > --- a/arch/x86/include/asm/mman.h > +++ b/arch/x86/include/asm/mman.h > @@ -20,11 +20,68 @@ > ((vm_flags) & VM_PKEY_BIT2 ? _PAGE_PKEY_BIT2 : 0) | \ > ((vm_flags) & VM_PKEY_BIT3 ? _PAGE_PKEY_BIT3 : 0)) > > -#define arch_calc_vm_prot_bits(prot, key) ( \ > +#define pkey_vm_prot_bits(prot, key) ( \ > ((key) & 0x1 ? VM_PKEY_BIT0 : 0) | \ > ((key) & 0x2 ? VM_PKEY_BIT1 : 0) | \ > ((key) & 0x4 ? VM_PKEY_BIT2 : 0) | \ > ((key) & 0x8 ? VM_PKEY_BIT3 : 0)) > +#else > +#define pkey_vm_prot_bits(prot, key) (0) > #endif > > +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, > + unsigned long pkey) > +{ > + unsigned long vm_prot_bits = pkey_vm_prot_bits(prot, pkey); > + > + if (prot & PROT_SHSTK) > + vm_prot_bits |= VM_SHADOW_STACK; > + > + return vm_prot_bits; > +} > + > +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) > + > +#ifdef CONFIG_X86_SHADOW_STACK > +static inline bool arch_validate_prot(unsigned long prot, unsigned long addr) > +{ > + unsigned long valid = PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | > + PROT_SHSTK; > + > + if (prot & ~valid) > + return false; > + > + if (prot & PROT_SHSTK) { > + if (!current->thread.cet.shstk_size) > + return false; > + > + /* > + * A shadow stack mapping is indirectly writable by only > + * the CALL and WRUSS instructions, but not other write > + * instructions). PROT_SHSTK and PROT_WRITE are mutually > + * exclusive. > + */ > + if (prot & PROT_WRITE) > + return false; > + } > + > + return true; > +} > + > +#define arch_validate_prot arch_validate_prot > + > +static inline bool arch_validate_flags(unsigned long vm_flags, bool is_anon) > +{ > + if (vm_flags & VM_SHADOW_STACK) { > + if ((vm_flags & VM_SHARED) || !is_anon) VM_SHARED check is redundant. vma_is_anonymous() should be enough. Anonymous shared mappings would fail vma_is_anonymous(). > + return false; > + } > + > + return true; > +} > + > +#define arch_validate_flags(vm_flags, is_anon) arch_validate_flags(vm_flags, is_anon) > + > +#endif /* CONFIG_X86_SHADOW_STACK */ > + > #endif /* _ASM_X86_MMAN_H */ > diff --git a/arch/x86/include/uapi/asm/mman.h b/arch/x86/include/uapi/asm/mman.h > index 3ce1923e6ed9..39bb7db344a6 100644 > --- a/arch/x86/include/uapi/asm/mman.h > +++ b/arch/x86/include/uapi/asm/mman.h > @@ -4,6 +4,7 @@ > > #define MAP_32BIT 0x40 /* only give out 32bit addresses */ > > +#define PROT_SHSTK 0x10 /* shadow stack pages */ > > #include > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 1ccec5cc399b..9a7652eea207 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -342,6 +342,7 @@ extern unsigned int kobjsize(const void *objp); > > #if defined(CONFIG_X86) > # define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */ > +# define VM_ARCH_CLEAR VM_SHADOW_STACK > #elif defined(CONFIG_PPC) > # define VM_SAO VM_ARCH_1 /* Strong Access Ordering (powerpc) */ > #elif defined(CONFIG_PARISC) > -- > 2.21.0 > > -- Kirill A. Shutemov