From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964816AbdDZSfK (ORCPT ); Wed, 26 Apr 2017 14:35:10 -0400 Received: from mail-pf0-f172.google.com ([209.85.192.172]:34472 "EHLO mail-pf0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936075AbdDZSe4 (ORCPT ); Wed, 26 Apr 2017 14:34:56 -0400 From: Thomas Garnier To: Martin Schwidefsky , Heiko Carstens , Dave Hansen , Arnd Bergmann , David Howells , =?UTF-8?q?Ren=C3=A9=20Nyffenegger?= , Thomas Garnier , Andrew Morton , "Paul E . McKenney" , Ingo Molnar , "Eric W . Biederman" , Thomas Gleixner , Oleg Nesterov , Pavel Tikhomirov , Ingo Molnar , "H . Peter Anvin" , Andy Lutomirski , Paolo Bonzini , Kees Cook , Rik van Riel , Josh Poimboeuf , Borislav Petkov , Brian Gerst , "Kirill A . Shutemov" , Christian Borntraeger , Russell King , Will Deacon , Catalin Marinas , Mark Rutland , James Morse Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, linux-arm-kernel@lists.infradead.org, kernel-hardening@lists.openwall.com Subject: [PATCH v8 4/4] arm64/syscalls: Optimize address limit check Date: Wed, 26 Apr 2017 11:34:25 -0700 Message-Id: <20170426183425.32158-4-thgarnie@google.com> X-Mailer: git-send-email 2.13.0.rc0.306.g87b477812d-goog In-Reply-To: <20170426183425.32158-1-thgarnie@google.com> References: <20170426183425.32158-1-thgarnie@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Disable the generic address limit check in favor of an architecture specific optimized implementation. The address limit is checked on each syscall return path to user-mode. If it was changed, a generic handler is called to stop the kernel on an explicit check. Signed-off-by: Thomas Garnier Reviewed-by: Catalin Marinas --- Based on next-20170426 --- arch/arm64/Kconfig | 1 + arch/arm64/kernel/entry.S | 12 ++++++++++++ 2 files changed, 13 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 3dcd7ec69bca..fe9466d3bf94 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -25,6 +25,7 @@ config ARM64 select ARCH_WANT_COMPAT_IPC_PARSE_VERSION select ARCH_WANT_FRAME_POINTERS select ARCH_HAS_UBSAN_SANITIZE_ALL + select ADDR_LIMIT_CHECK select ARM_AMBA select ARM_ARCH_TIMER select ARM_GIC diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 43512d4d7df2..c895c4402d32 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -744,6 +744,8 @@ ENDPROC(cpu_switch_to) ret_fast_syscall: disable_irq // disable interrupts str x0, [sp, #S_X0] // returned x0 + ldr x2, [tsk, #TSK_TI_ADDR_LIMIT] // check addr limit change + tbnz x2, #63, addr_limit_fail ldr x1, [tsk, #TSK_TI_FLAGS] // re-check for syscall tracing and x2, x1, #_TIF_SYSCALL_WORK cbnz x2, ret_fast_syscall_trace @@ -771,6 +773,8 @@ work_pending: */ ret_to_user: disable_irq // disable interrupts + ldr x2, [tsk, #TSK_TI_ADDR_LIMIT] // check addr limit change + tbnz x2, #63, addr_limit_fail ldr x1, [tsk, #TSK_TI_FLAGS] and x2, x1, #_TIF_WORK_MASK cbnz x2, work_pending @@ -780,6 +784,14 @@ finish_ret_to_user: ENDPROC(ret_to_user) /* + * Address limit was incorrect before returning in user-mode which could be + * used to elevate privileges. Call the generic handler to stop the kernel on + * the appropriate check. This function does not return. + */ +addr_limit_fail: + b addr_limit_check_failed + +/* * This is how we return from a fork. */ ENTRY(ret_from_fork) -- 2.13.0.rc0.306.g87b477812d-goog