From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yu-cheng Yu Subject: [RFC PATCH v4 22/27] x86/cet/shstk: Handle thread shadow stack Date: Fri, 21 Sep 2018 08:03:46 -0700 Message-ID: <20180921150351.20898-23-yu-cheng.yu@intel.com> References: <20180921150351.20898-1-yu-cheng.yu@intel.com> Return-path: In-Reply-To: <20180921150351.20898-1-yu-cheng.yu@intel.com> Sender: linux-kernel-owner@vger.kernel.org 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 Cc: Yu-cheng Yu List-Id: linux-arch.vger.kernel.org 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 ea5ea850348d..9cdbd87bb908 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -325,6 +325,13 @@ 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, -- 2.17.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com ([192.55.52.93]:13578 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390470AbeIUU6K (ORCPT ); Fri, 21 Sep 2018 16:58:10 -0400 From: Yu-cheng Yu Subject: [RFC PATCH v4 22/27] x86/cet/shstk: Handle thread shadow stack Date: Fri, 21 Sep 2018 08:03:46 -0700 Message-ID: <20180921150351.20898-23-yu-cheng.yu@intel.com> In-Reply-To: <20180921150351.20898-1-yu-cheng.yu@intel.com> References: <20180921150351.20898-1-yu-cheng.yu@intel.com> Sender: linux-arch-owner@vger.kernel.org List-ID: 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 , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue Cc: Yu-cheng Yu Message-ID: <20180921150346.LZ4cs0P4mIVpBbvFvWsxrgxODpqKwF0v_w27qTVsI9w@z> 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 ea5ea850348d..9cdbd87bb908 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -325,6 +325,13 @@ 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, -- 2.17.1