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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 38FA4C8300F for ; Wed, 29 Apr 2020 22:09:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id ECAF921D7A for ; Wed, 29 Apr 2020 22:09:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ECAF921D7A 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 28B5F8E001F; Wed, 29 Apr 2020 18:08:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 19D838E001D; Wed, 29 Apr 2020 18:08:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 08A9E8E001E; Wed, 29 Apr 2020 18:08:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0054.hostedemail.com [216.40.44.54]) by kanga.kvack.org (Postfix) with ESMTP id DD9CE8E001A for ; Wed, 29 Apr 2020 18:08:56 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A228152BF for ; Wed, 29 Apr 2020 22:08:56 +0000 (UTC) X-FDA: 76762283472.13.uncle52_13cac9aee3d22 X-HE-Tag: uncle52_13cac9aee3d22 X-Filterd-Recvd-Size: 7126 Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by imf44.hostedemail.com (Postfix) with ESMTP for ; Wed, 29 Apr 2020 22:08:55 +0000 (UTC) IronPort-SDR: tGMhCrmyai17RwB9P8gxQwUNrVfBEnMo1aS2rt4jm395JMPvV7iarmWVJ5Th16xy8ahHicjuHr gwinTCu3eOxQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Apr 2020 15:08:55 -0700 IronPort-SDR: 9gcKwhvbHzr2PzbwK7j19tLnl6PrCaK1/7js6IHdj4K0we/ZoBaCVwpdjZoRrKOe24btfX7Xgn zqpM34nLw8zg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,333,1583222400"; d="scan'208";a="276308941" Received: from yyu32-desk.sc.intel.com ([143.183.136.146]) by orsmga002.jf.intel.com with ESMTP; 29 Apr 2020 15:08:54 -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 Cc: Yu-cheng Yu Subject: [PATCH v10 25/26] x86/cet/shstk: Handle thread shadow stack Date: Wed, 29 Apr 2020 15:07:31 -0700 Message-Id: <20200429220732.31602-26-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200429220732.31602-1-yu-cheng.yu@intel.com> References: <20200429220732.31602-1-yu-cheng.yu@intel.com> MIME-Version: 1.0 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. A 64-bit shadow stack has a size of min(RLIMIT_STACK, 4 GB). A compat-mo= de thread shadow stack has a size of 1/4 min(RLIMIT_STACK, 4 GB). This allo= ws more threads to run in a 32-bit address space. Signed-off-by: Yu-cheng Yu --- v10: - Limit shadow stack size to 4 GB. arch/x86/include/asm/cet.h | 2 ++ arch/x86/include/asm/mmu_context.h | 3 +++ arch/x86/kernel/cet.c | 41 ++++++++++++++++++++++++++++++ arch/x86/kernel/process.c | 7 +++++ 4 files changed, 53 insertions(+) diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h index 56fe08eebae6..71dc92acd2f2 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -18,11 +18,13 @@ struct cet_status { =20 #ifdef CONFIG_X86_INTEL_CET int cet_setup_shstk(void); +int cet_setup_thread_shstk(struct task_struct *p); void cet_disable_free_shstk(struct task_struct *p); int cet_verify_rstor_token(bool ia32, unsigned long ssp, unsigned long *= new_ssp); void cet_restore_signal(struct sc_ext *sc); int cet_setup_signal(bool ia32, unsigned long rstor, struct sc_ext *sc); #else +static inline int cet_setup_thread_shstk(struct task_struct *p) { return= 0; } static inline void cet_disable_free_shstk(struct task_struct *p) {} static inline void cet_restore_signal(struct sc_ext *sc) { return; } static inline int cet_setup_signal(bool ia32, unsigned long rstor, diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mm= u_context.h index 4e55370e48e8..bb7a4a2d6923 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -12,6 +12,7 @@ #include #include #include +#include #include =20 extern atomic64_t last_mm_ctx_id; @@ -155,6 +156,8 @@ do { \ #else #define deactivate_mm(tsk, mm) \ do { \ + if (!tsk->vfork_done) \ + cet_disable_free_shstk(tsk); \ load_gs_index(0); \ loadsegment(fs, 0); \ } while (0) diff --git a/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c index 274fecdd9669..121552047b86 100644 --- a/arch/x86/kernel/cet.c +++ b/arch/x86/kernel/cet.c @@ -169,6 +169,47 @@ int cet_setup_shstk(void) return 0; } =20 +int cet_setup_thread_shstk(struct task_struct *tsk) +{ + unsigned long addr, size; + struct cet_user_state *state; + struct cet_status *cet =3D &tsk->thread.cet; + + if (!cet->shstk_size) + return 0; + + state =3D get_xsave_addr(&tsk->thread.fpu.state.xsave, + XFEATURE_CET_USER); + + if (!state) + return -EINVAL; + + /* Cap shadow stack size to 4 GB */ + size =3D min(rlimit(RLIMIT_STACK), 1UL << 32); + + /* + * Compat-mode pthreads share a limited address space. + * If each function call takes an average of four slots + * stack space, we need 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); + + if (IS_ERR((void *)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 cet_disable_free_shstk(struct task_struct *tsk) { struct cet_status *cet =3D &tsk->thread.cet; diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 9d9cff2c1018..ef1c2b8086a2 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -109,6 +109,7 @@ void exit_thread(struct task_struct *tsk) =20 free_vm86(t); =20 + cet_disable_free_shstk(tsk); fpu__drop(fpu); } =20 @@ -179,6 +180,12 @@ int copy_thread_tls(unsigned long clone_flags, unsig= ned long sp, 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 && (clone_flags & (CLONE_VFORK | CLONE_VM)) =3D=3D CLONE_VM) + ret =3D cet_setup_thread_shstk(p); +#endif + if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP))) io_bitmap_share(p); =20 --=20 2.21.0