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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 780CCC43461 for ; Mon, 10 May 2021 14:17:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5003A610F8 for ; Mon, 10 May 2021 14:17:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241865AbhEJOSw (ORCPT ); Mon, 10 May 2021 10:18:52 -0400 Received: from mail.skyhub.de ([5.9.137.197]:59686 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232009AbhEJORD (ORCPT ); Mon, 10 May 2021 10:17:03 -0400 Received: from zn.tnic (p200300ec2f066d00159cc50318b4d41b.dip0.t-ipconnect.de [IPv6:2003:ec:2f06:6d00:159c:c503:18b4:d41b]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 3CCFD1EC0350; Mon, 10 May 2021 16:15:46 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1620656146; h=from:from: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; bh=o2aoaH2RymU6wxi8X7V+6fjKICNEkCYu8vfZLJTg/WM=; b=r4xTua/evyV7MIbUF+KfrYv8m7oot0Y5Z+nHZRk9uPtU1XfbM2yO8UnOjpCQOMi8FzBIwA PUewBV0RTv/uqtgZbIlCXnskJ1wspzZu6DiFOn9gKpKLxni5yqrf3Pk2xKgia/oY21j8pf PjDV2UJsf4y20ufm418bw+P+7VMh8O4= Date: Mon, 10 May 2021 16:15:43 +0200 From: Borislav Petkov 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 , 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 Subject: Re: [PATCH v26 23/30] x86/cet/shstk: Handle thread shadow stack Message-ID: References: <20210427204315.24153-1-yu-cheng.yu@intel.com> <20210427204315.24153-24-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210427204315.24153-24-yu-cheng.yu@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 27, 2021 at 01:43:08PM -0700, Yu-cheng Yu wrote: > @@ -181,6 +184,12 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg, > if (clone_flags & CLONE_SETTLS) > ret = set_new_tls(p, tls); > > +#ifdef CONFIG_X86_64 IS_ENABLED > + /* Allocate a new shadow stack for pthread */ > + if (!ret) > + ret = shstk_setup_thread(p, clone_flags, stack_size); > +#endif > + And why is this addition here... > if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP))) > io_bitmap_share(p); ... instead of here? <--- > > diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c > index c815c7507830..d387df84b7f1 100644 > --- a/arch/x86/kernel/shstk.c > +++ b/arch/x86/kernel/shstk.c > @@ -70,6 +70,55 @@ int shstk_setup(void) > return 0; > } > +int shstk_setup_thread(struct task_struct *tsk, unsigned long clone_flags, Judging by what this function does, its name wants to be shstk_alloc_thread_stack() or so? > + unsigned long stack_size) > +{ > + unsigned long addr, size; > + struct cet_user_state *state; > + struct cet_status *cet = &tsk->thread.cet; The tip-tree preferred ordering of variable declarations at the beginning of a function is reverse fir tree order:: struct long_struct_name *descriptive_name; unsigned long foo, bar; unsigned int tmp; int ret; The above is faster to parse than the reverse ordering:: int ret; unsigned int tmp; unsigned long foo, bar; struct long_struct_name *descriptive_name; And even more so than random ordering:: unsigned long foo, bar; int ret; struct long_struct_name *descriptive_name; unsigned int tmp; > + > + if (!cet->shstk_size) > + return 0; > + This check needs a comment. > + if ((clone_flags & (CLONE_VFORK | CLONE_VM)) != CLONE_VM) > + return 0; > + > + state = get_xsave_addr(&tsk->thread.fpu.state.xsave, > + XFEATURE_CET_USER); Let that line stick out. > + > + if (!state) > + return -EINVAL; > + > + if (stack_size == 0) if (!stack_size) > + return -EINVAL; and that test needs to be done first in the function. > + > + /* Cap shadow stack size to 4 GB */ Why? > + size = min_t(unsigned long long, rlimit(RLIMIT_STACK), SZ_4G); > + size = min(size, stack_size); > + > + /* > + * Compat-mode pthreads share a limited address space. > + * If each function call takes an average of four slots > + * stack space, allocate 1/4 of stack size for shadow stack. > + */ > + if (in_compat_syscall()) > + size /= 4; <---- newline here. > + size = round_up(size, PAGE_SIZE); > + addr = alloc_shstk(size); > + ^ Superfluous newline. > + if (IS_ERR_VALUE(addr)) { > + cet->shstk_base = 0; > + cet->shstk_size = 0; > + return PTR_ERR((void *)addr); > + } > + > + fpu__prepare_write(&tsk->thread.fpu); > + state->user_ssp = (u64)(addr + size); cet_user_state has u64, cet_status has unsigned longs. Make them all u64. And since cet_status is per thread, but I had suggested struct shstk_desc, I think now that that should be called struct thread_shstk or so to denote *exactly* what it is. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette