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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 75D38C43460 for ; Thu, 1 Apr 2021 22:12:08 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 16A11610FA for ; Thu, 1 Apr 2021 22:12:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 16A11610FA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0E7ED6B0102; Thu, 1 Apr 2021 18:11:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 097926B0105; Thu, 1 Apr 2021 18:11:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E7BBF6B0104; Thu, 1 Apr 2021 18:11:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id C515A6B0102 for ; Thu, 1 Apr 2021 18:11:30 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 8922F1839A9DA for ; Thu, 1 Apr 2021 22:11:30 +0000 (UTC) X-FDA: 77985195540.16.2D94784 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by imf24.hostedemail.com (Postfix) with ESMTP id 32413A000391 for ; Thu, 1 Apr 2021 22:11:28 +0000 (UTC) IronPort-SDR: CDwdK14Hz8xGkDlfEGAmbS41YRzqTIOygbGNG6oXTNl9TXPVo6twVjFVrIgODhoTWoUI6UOcGh KEEz9AGCo/iA== X-IronPort-AV: E=McAfee;i="6000,8403,9941"; a="192371418" X-IronPort-AV: E=Sophos;i="5.81,296,1610438400"; d="scan'208";a="192371418" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2021 15:11:26 -0700 IronPort-SDR: ft1CyQwBXyx1gHhH3zf+r3pe4lXQwkb2xoEld/NiqZ09pdkvKiR6Gf11TT3yXXo0VUr5SKfxXF 2EEQ2sH76Rxg== X-IronPort-AV: E=Sophos;i="5.81,296,1610438400"; d="scan'208";a="517513942" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by fmsmga001-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2021 15:11:25 -0700 From: Yu-cheng Yu To: 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 Cc: Yu-cheng Yu Subject: [PATCH v24 23/30] x86/cet/shstk: Handle thread shadow stack Date: Thu, 1 Apr 2021 15:10:57 -0700 Message-Id: <20210401221104.31584-24-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20210401221104.31584-1-yu-cheng.yu@intel.com> References: <20210401221104.31584-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 32413A000391 X-Stat-Signature: qr1yx8rh1hbbzd3sj7gzwnncnyeub5kh X-Rspamd-Server: rspam02 Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf24; identity=mailfrom; envelope-from=""; helo=mga03.intel.com; client-ip=134.134.136.65 X-HE-DKIM-Result: none/none X-HE-Tag: 1617315088-131394 Content-Transfer-Encoding: quoted-printable 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: The kernel allocates (and frees on thread exit) a new shadow stack for a pthread child. It is possible for the kernel to complete the clone syscall and set t= he child's shadow stack pointer to NULL and let the child thread allocat= e a shadow stack for itself. There are two issues in this approach: It is not compatible with existing code that does inline syscall and it cannot handle signals before the child can successfully allocate a shadow stack. Use stack_size passed from clone3() syscall for thread shadow stack size, but cap it to min(RLIMIT_STACK, 4 GB). A compat-mode thread shadow stack size is further reduced to 1/4. This allows more threads to run in a 32- bit address space. Signed-off-by: Yu-cheng Yu --- arch/x86/include/asm/cet.h | 5 +++ arch/x86/include/asm/mmu_context.h | 3 ++ arch/x86/kernel/process.c | 15 ++++++-- arch/x86/kernel/shstk.c | 57 +++++++++++++++++++++++++++++- 4 files changed, 76 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h index aa85d599b184..8b83ded577cc 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -16,10 +16,15 @@ struct cet_status { =20 #ifdef CONFIG_X86_SHADOW_STACK int shstk_setup(void); +int shstk_setup_thread(struct task_struct *p, unsigned long clone_flags, + unsigned long stack_size); void shstk_free(struct task_struct *p); void shstk_disable(void); #else static inline int shstk_setup(void) { return 0; } +static inline int shstk_setup_thread(struct task_struct *p, + unsigned long clone_flags, + unsigned long stack_size) { return 0; } static inline void shstk_free(struct task_struct *p) {} static inline void shstk_disable(void) {} #endif diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mm= u_context.h index 27516046117a..53569114aa01 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -11,6 +11,7 @@ =20 #include #include +#include #include =20 extern atomic64_t last_mm_ctx_id; @@ -146,6 +147,8 @@ do { \ #else #define deactivate_mm(tsk, mm) \ do { \ + if (!tsk->vfork_done) \ + shstk_free(tsk); \ load_gs_index(0); \ loadsegment(fs, 0); \ } while (0) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 9c214d7085a4..fa01e8679d01 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -43,6 +43,7 @@ #include #include #include +#include =20 #include "process.h" =20 @@ -109,6 +110,7 @@ void exit_thread(struct task_struct *tsk) =20 free_vm86(t); =20 + shstk_free(tsk); fpu__drop(fpu); } =20 @@ -122,8 +124,9 @@ static int set_new_tls(struct task_struct *p, unsigne= d long tls) return do_set_thread_area_64(p, ARCH_SET_FS, tls); } =20 -int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned lo= ng arg, - struct task_struct *p, unsigned long tls) +int copy_thread(unsigned long clone_flags, unsigned long sp, + unsigned long stack_size, struct task_struct *p, + unsigned long tls) { struct inactive_task_frame *frame; struct fork_frame *fork_frame; @@ -163,7 +166,7 @@ int copy_thread(unsigned long clone_flags, unsigned l= ong sp, unsigned long arg, /* Kernel thread ? */ if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) { memset(childregs, 0, sizeof(struct pt_regs)); - kthread_frame_init(frame, sp, arg); + kthread_frame_init(frame, sp, stack_size); return 0; } =20 @@ -181,6 +184,12 @@ int copy_thread(unsigned long clone_flags, unsigned = long sp, unsigned long arg, if (clone_flags & CLONE_SETTLS) ret =3D set_new_tls(p, tls); =20 +#ifdef CONFIG_X86_64 + /* Allocate a new shadow stack for pthread */ + if (!ret) + ret =3D shstk_setup_thread(p, clone_flags, stack_size); +#endif + if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP))) io_bitmap_share(p); =20 diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 5406fdf6df3c..9c80785535b9 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -75,6 +75,55 @@ int shstk_setup(void) return 0; } =20 +int shstk_setup_thread(struct task_struct *tsk, unsigned long clone_flag= s, + unsigned long stack_size) +{ + unsigned long addr, size; + struct cet_user_state *state; + struct cet_status *cet =3D &tsk->thread.cet; + + if (!cet->shstk_size) + return 0; + + if ((clone_flags & (CLONE_VFORK | CLONE_VM)) !=3D CLONE_VM) + return 0; + + state =3D get_xsave_addr(&tsk->thread.fpu.state.xsave, + XFEATURE_CET_USER); + + if (!state) + return -EINVAL; + + if (stack_size =3D=3D 0) + return -EINVAL; + + /* Cap shadow stack size to 4 GB */ + size =3D min_t(unsigned long long, rlimit(RLIMIT_STACK), SZ_4G); + size =3D 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 /=3D 4; + size =3D round_up(size, PAGE_SIZE); + addr =3D alloc_shstk(size, 0); + + if (IS_ERR_VALUE(addr)) { + cet->shstk_base =3D 0; + cet->shstk_size =3D 0; + return PTR_ERR((void *)addr); + } + + fpu__prepare_write(&tsk->thread.fpu); + state->user_ssp =3D (u64)(addr + size); + cet->shstk_base =3D addr; + cet->shstk_size =3D size; + return 0; +} + void shstk_free(struct task_struct *tsk) { struct cet_status *cet =3D &tsk->thread.cet; @@ -84,7 +133,13 @@ void shstk_free(struct task_struct *tsk) !cet->shstk_base) return; =20 - if (!tsk->mm) + /* + * When fork() with CLONE_VM fails, the child (tsk) already has a + * shadow stack allocated, and exit_thread() calls this function to + * free it. In this case the parent (current) and the child is + * sharing the same mm struct. + */ + if (!tsk->mm || tsk->mm !=3D current->mm) return; =20 while (1) { --=20 2.21.0