From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752533AbdHNViI (ORCPT ); Mon, 14 Aug 2017 17:38:08 -0400 Received: from mail-pg0-f50.google.com ([74.125.83.50]:38352 "EHLO mail-pg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752290AbdHNViF (ORCPT ); Mon, 14 Aug 2017 17:38:05 -0400 From: Thomas Garnier To: Al Viro , Dave Hansen , Arnd Bergmann , Thomas Gleixner , Thomas Garnier , Yonghong Song , David Howells , Russell King , Kees Cook , Andy Lutomirski , Will Drewry , Dave Martin , Catalin Marinas , Will Deacon Cc: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kernel-hardening@lists.openwall.com Subject: [PATCH v3 1/4] syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check Date: Mon, 14 Aug 2017 14:37:29 -0700 Message-Id: <20170814213732.104301-1-thgarnie@google.com> X-Mailer: git-send-email 2.14.1.480.gb18f417b89-goog Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Use CHECK_DATA_CORRUPTION instead of BUG_ON to provide more flexibility on address limit failures. By default, send a SIGKILL signal to kill the current process preventing exploitation of a bad address limit. Make the TIF_FSCHECK flag optional so ARM can use this function. Signed-off-by: Thomas Garnier --- include/linux/syscalls.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 88951b795ee3..65e273aadada 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -219,21 +219,25 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event) } \ static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__)) -#ifdef TIF_FSCHECK /* * Called before coming back to user-mode. Returning to user-mode with an * address limit different than USER_DS can allow to overwrite kernel memory. */ static inline void addr_limit_user_check(void) { - +#ifdef TIF_FSCHECK if (!test_thread_flag(TIF_FSCHECK)) return; +#endif - BUG_ON(!segment_eq(get_fs(), USER_DS)); + if (CHECK_DATA_CORRUPTION(!segment_eq(get_fs(), USER_DS), + "Invalid address limit on user-mode return")) + force_sig(SIGKILL, current); + +#ifdef TIF_FSCHECK clear_thread_flag(TIF_FSCHECK); -} #endif +} asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special, qid_t id, void __user *addr); -- 2.14.1.480.gb18f417b89-goog