From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755571AbdIGPcL (ORCPT ); Thu, 7 Sep 2017 11:32:11 -0400 Received: from mail-pg0-f50.google.com ([74.125.83.50]:38853 "EHLO mail-pg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754105AbdIGPbC (ORCPT ); Thu, 7 Sep 2017 11:31:02 -0400 X-Google-Smtp-Source: ADKCNb7F/heq6IJdbwciFp5DgJnSicFnY+4fqx/m8wH+y+7TLz8kCulvtd8WkaYo4r6Pk+8GN7aZUw== From: Kees Cook To: Ingo Molnar Cc: Kees Cook , Thomas Garnier , Thomas Gleixner , Russell King , Catalin Marinas , Will Deacon , Andy Lutomirski , Will Drewry , Al Viro , Dave Martin , Pratyush Anand , Dave Hansen , Arnd Bergmann , David Howells , Yonghong Song , linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/4] arm/syscalls: Optimize address limit check Date: Thu, 7 Sep 2017 08:30:46 -0700 Message-Id: <1504798247-48833-4-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1504798247-48833-1-git-send-email-keescook@chromium.org> References: <1504798247-48833-1-git-send-email-keescook@chromium.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Thomas Garnier Disable the generic address limit check in favor of an architecture specific optimized implementation. The generic implementation using pending work flags did not work well with ARM and alignment faults. The address limit is checked on each syscall return path to user-mode path as well as the irq user-mode return function. If the address limit was changed, a function is called to report data corruption (stopping the kernel or process based on configuration). The address limit check has to be done before any pending work because they can reset the address limit and the process is killed using a SIGKILL signal. For example the lkdtm address limit check does not work because the signal to kill the process will reset the user-mode address limit. Signed-off-by: Thomas Garnier Reviewed-by: Kees Cook Tested-by: Kees Cook Tested-by: Leonard Crestez Signed-off-by: Kees Cook --- arch/arm/kernel/entry-common.S | 11 +++++++++++ arch/arm/kernel/signal.c | 7 +++++++ 2 files changed, 18 insertions(+) diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index eb5cd77bf1d8..126fafc725bc 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -12,6 +12,7 @@ #include #include #include +#include #ifdef CONFIG_AEABI #include #endif @@ -40,10 +41,14 @@ ret_fast_syscall: UNWIND(.fnstart ) UNWIND(.cantunwind ) disable_irq_notrace @ disable interrupts + ldr r2, [tsk, #TI_ADDR_LIMIT] + cmp r2, #TASK_SIZE + blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK bne fast_work_pending + /* perform architecture specific actions before user return */ arch_ret_to_user r1, lr @@ -66,6 +71,9 @@ ret_fast_syscall: UNWIND(.cantunwind ) str r0, [sp, #S_R0 + S_OFF]! @ save returned r0 disable_irq_notrace @ disable interrupts + ldr r2, [tsk, #TI_ADDR_LIMIT] + cmp r2, #TASK_SIZE + blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK beq no_work_pending @@ -98,6 +106,9 @@ ENTRY(ret_to_user) ret_slow_syscall: disable_irq_notrace @ disable interrupts ENTRY(ret_to_user_from_irq) + ldr r2, [tsk, #TI_ADDR_LIMIT] + cmp r2, #TASK_SIZE + blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] tst r1, #_TIF_WORK_MASK bne slow_work_pending diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index 5814298ef0b7..b67ae12503f3 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -673,3 +674,9 @@ struct page *get_signal_page(void) return page; } + +/* Defer to generic check */ +asmlinkage void addr_limit_check_failed(void) +{ + addr_limit_user_check(); +} -- 2.7.4 From mboxrd@z Thu Jan 1 00:00:00 1970 From: keescook@chromium.org (Kees Cook) Date: Thu, 7 Sep 2017 08:30:46 -0700 Subject: [PATCH 3/4] arm/syscalls: Optimize address limit check In-Reply-To: <1504798247-48833-1-git-send-email-keescook@chromium.org> References: <1504798247-48833-1-git-send-email-keescook@chromium.org> Message-ID: <1504798247-48833-4-git-send-email-keescook@chromium.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Thomas Garnier Disable the generic address limit check in favor of an architecture specific optimized implementation. The generic implementation using pending work flags did not work well with ARM and alignment faults. The address limit is checked on each syscall return path to user-mode path as well as the irq user-mode return function. If the address limit was changed, a function is called to report data corruption (stopping the kernel or process based on configuration). The address limit check has to be done before any pending work because they can reset the address limit and the process is killed using a SIGKILL signal. For example the lkdtm address limit check does not work because the signal to kill the process will reset the user-mode address limit. Signed-off-by: Thomas Garnier Reviewed-by: Kees Cook Tested-by: Kees Cook Tested-by: Leonard Crestez Signed-off-by: Kees Cook --- arch/arm/kernel/entry-common.S | 11 +++++++++++ arch/arm/kernel/signal.c | 7 +++++++ 2 files changed, 18 insertions(+) diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index eb5cd77bf1d8..126fafc725bc 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -12,6 +12,7 @@ #include #include #include +#include #ifdef CONFIG_AEABI #include #endif @@ -40,10 +41,14 @@ ret_fast_syscall: UNWIND(.fnstart ) UNWIND(.cantunwind ) disable_irq_notrace @ disable interrupts + ldr r2, [tsk, #TI_ADDR_LIMIT] + cmp r2, #TASK_SIZE + blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK bne fast_work_pending + /* perform architecture specific actions before user return */ arch_ret_to_user r1, lr @@ -66,6 +71,9 @@ ret_fast_syscall: UNWIND(.cantunwind ) str r0, [sp, #S_R0 + S_OFF]! @ save returned r0 disable_irq_notrace @ disable interrupts + ldr r2, [tsk, #TI_ADDR_LIMIT] + cmp r2, #TASK_SIZE + blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] @ re-check for syscall tracing tst r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK beq no_work_pending @@ -98,6 +106,9 @@ ENTRY(ret_to_user) ret_slow_syscall: disable_irq_notrace @ disable interrupts ENTRY(ret_to_user_from_irq) + ldr r2, [tsk, #TI_ADDR_LIMIT] + cmp r2, #TASK_SIZE + blne addr_limit_check_failed ldr r1, [tsk, #TI_FLAGS] tst r1, #_TIF_WORK_MASK bne slow_work_pending diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c index 5814298ef0b7..b67ae12503f3 100644 --- a/arch/arm/kernel/signal.c +++ b/arch/arm/kernel/signal.c @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -673,3 +674,9 @@ struct page *get_signal_page(void) return page; } + +/* Defer to generic check */ +asmlinkage void addr_limit_check_failed(void) +{ + addr_limit_user_check(); +} -- 2.7.4