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[192.55.52.88]) by mx.google.com with ESMTPS id w13-v6si6403728pll.449.2018.08.30.07.43.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Aug 2018 07:43:46 -0700 (PDT) Received-SPF: pass (google.com: domain of yu-cheng.yu@intel.com designates 192.55.52.88 as permitted sender) client-ip=192.55.52.88; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yu-cheng.yu@intel.com designates 192.55.52.88 as permitted sender) smtp.mailfrom=yu-cheng.yu@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 30 Aug 2018 07:43:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,307,1531810800"; d="scan'208";a="67186733" Received: from 2b52.sc.intel.com ([143.183.136.52]) by fmsmga008.fm.intel.com with ESMTP; 30 Aug 2018 07:43:43 -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 , Cyrill Gorcunov , Dave Hansen , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , "Ravi V. Shankar" , Vedvyas Shanbhogue Cc: Yu-cheng Yu Subject: [RFC PATCH v3 22/24] x86/cet/shstk: Handle thread shadow stack Date: Thu, 30 Aug 2018 07:39:02 -0700 Message-Id: <20180830143904.3168-23-yu-cheng.yu@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180830143904.3168-1-yu-cheng.yu@intel.com> References: <20180830143904.3168-1-yu-cheng.yu@intel.com> 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: X-Virus-Scanned: ClamAV using ClamSMTP The shadow stack for clone/fork is handled as the following: (1) If ((clone_flags & (CLONE_VFORK | CLONE_VM)) == CLONE_VM), the kernel allocates (and frees on thread exit) a new SHSTK for the child. It is possible for the kernel to complete the clone syscall and set the child's SHSTK pointer to NULL and let the child thread allocate a SHSTK 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 SHSTK. (2) For (clone_flags & CLONE_VFORK), the child uses the existing SHSTK. (3) For all other cases, the SHSTK is copied/reused whenever the parent or the child does a call/ret. This patch handles cases (1) & (2). Case (3) is handled in the SHSTK page fault patches. Signed-off-by: Yu-cheng Yu --- arch/x86/include/asm/cet.h | 2 ++ arch/x86/include/asm/mmu_context.h | 3 +++ arch/x86/kernel/cet.c | 34 ++++++++++++++++++++++++++++++ arch/x86/kernel/process.c | 1 + arch/x86/kernel/process_64.c | 7 ++++++ 5 files changed, 47 insertions(+) diff --git a/arch/x86/include/asm/cet.h b/arch/x86/include/asm/cet.h index d9ae3d86cdd7..b7b33e1026bb 100644 --- a/arch/x86/include/asm/cet.h +++ b/arch/x86/include/asm/cet.h @@ -17,12 +17,14 @@ struct cet_status { #ifdef CONFIG_X86_INTEL_CET int cet_setup_shstk(void); +int cet_setup_thread_shstk(struct task_struct *p); void cet_disable_shstk(void); void cet_disable_free_shstk(struct task_struct *p); int cet_restore_signal(unsigned long ssp); int cet_setup_signal(bool ia32, unsigned long rstor, unsigned long *new_ssp); #else static inline int cet_setup_shstk(void) { return 0; } +static inline int cet_setup_thread_shstk(struct task_struct *p) { return 0; } static inline void cet_disable_shstk(void) {} static inline void cet_disable_free_shstk(struct task_struct *p) {} static inline int cet_restore_signal(unsigned long ssp) { return 0; } diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index eeeb9289c764..8da7c999b7ee 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -13,6 +13,7 @@ #include #include #include +#include extern atomic64_t last_mm_ctx_id; @@ -223,6 +224,8 @@ 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 5cc4be6e0982..ce0b3b7b1160 100644 --- a/arch/x86/kernel/cet.c +++ b/arch/x86/kernel/cet.c @@ -134,6 +134,40 @@ int cet_setup_shstk(void) return 0; } +int cet_setup_thread_shstk(struct task_struct *tsk) +{ + unsigned long addr, size; + struct cet_user_state *state; + + if (!current->thread.cet.shstk_enabled) + return 0; + + state = get_xsave_addr(&tsk->thread.fpu.state.xsave, + XFEATURE_MASK_SHSTK_USER); + + if (!state) + return -EINVAL; + + size = tsk->thread.cet.shstk_size; + if (size == 0) + size = rlimit(RLIMIT_STACK); + + addr = do_mmap_locked(0, size, PROT_READ, + MAP_ANONYMOUS | MAP_PRIVATE, VM_SHSTK); + + if (addr >= TASK_SIZE_MAX) { + tsk->thread.cet.shstk_base = 0; + tsk->thread.cet.shstk_size = 0; + tsk->thread.cet.shstk_enabled = 0; + return -ENOMEM; + } + + state->user_ssp = (u64)(addr + size - sizeof(u64)); + tsk->thread.cet.shstk_base = addr; + tsk->thread.cet.shstk_size = size; + return 0; +} + void cet_disable_shstk(void) { u64 r; diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 4a776da4c28c..440f012ef925 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -125,6 +125,7 @@ void exit_thread(struct task_struct *tsk) free_vm86(t); + cet_disable_free_shstk(tsk); fpu__drop(fpu); } diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index a451bc374b9b..cfe955d8d6b2 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -317,6 +317,13 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp, if (sp) childregs->sp = sp; + /* Allocate a new shadow stack for pthread */ + if ((clone_flags & (CLONE_VFORK | CLONE_VM)) == CLONE_VM) { + err = cet_setup_thread_shstk(p); + if (err) + goto out; + } + err = -ENOMEM; if (unlikely(test_tsk_thread_flag(me, TIF_IO_BITMAP))) { p->thread.io_bitmap_ptr = kmemdup(me->thread.io_bitmap_ptr,