From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45944 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728587AbeICVr4 (ORCPT ); Mon, 3 Sep 2018 17:47:56 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , Thomas Gleixner , Andrey Ryabinin , Andy Lutomirski , Dmitry Vyukov , Alexander Potapenko , Kees Cook , kasan-dev@googlegroups.com Subject: [PATCH 4.14 141/165] x86/entry/64: Wipe KASAN stack shadow before rewind_stack_do_exit() Date: Mon, 3 Sep 2018 18:57:07 +0200 Message-Id: <20180903165702.609367627@linuxfoundation.org> In-Reply-To: <20180903165655.003605184@linuxfoundation.org> References: <20180903165655.003605184@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jann Horn commit f12d11c5c184626b4befdee3d573ec8237405a33 upstream. Reset the KASAN shadow state of the task stack before rewinding RSP. Without this, a kernel oops will leave parts of the stack poisoned, and code running under do_exit() can trip over such poisoned regions and cause nonsensical false-positive KASAN reports about stack-out-of-bounds bugs. This does not wipe the exception stacks; if an oops happens on an exception stack, it might result in random KASAN false-positives from other tasks afterwards. This is probably relatively uninteresting, since if the kernel oopses on an exception stack, there are most likely bigger things to worry about. It'd be more interesting if vmapped stacks and KASAN were compatible, since then handle_stack_overflow() would oops from exception stack context. Fixes: 2deb4be28077 ("x86/dumpstack: When OOPSing, rewind the stack before do_exit()") Signed-off-by: Jann Horn Signed-off-by: Thomas Gleixner Acked-by: Andrey Ryabinin Cc: Andy Lutomirski Cc: Dmitry Vyukov Cc: Alexander Potapenko Cc: Kees Cook Cc: kasan-dev@googlegroups.com Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180828184033.93712-1-jannh@google.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/dumpstack.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include @@ -298,7 +299,10 @@ void oops_end(unsigned long flags, struc * We're not going to return, but we might be on an IST stack or * have very little stack space left. Rewind the stack and kill * the task. + * Before we rewind the stack, we have to tell KASAN that we're going to + * reuse the task stack and that existing poisons are invalid. */ + kasan_unpoison_task_stack(current); rewind_stack_do_exit(signr); } NOKPROBE_SYMBOL(oops_end);