From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754702AbdK1Lmw (ORCPT ); Tue, 28 Nov 2017 06:42:52 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:60446 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752123AbdK1KmT (ORCPT ); Tue, 28 Nov 2017 05:42:19 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Christian Borntraeger , Heiko Carstens , Martin Schwidefsky Subject: [PATCH 4.14 003/193] s390/runtime instrumention: fix possible memory corruption Date: Tue, 28 Nov 2017 11:24:10 +0100 Message-Id: <20171128100613.803168559@linuxfoundation.org> X-Mailer: git-send-email 2.15.0 In-Reply-To: <20171128100613.638270407@linuxfoundation.org> References: <20171128100613.638270407@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Heiko Carstens commit d6e646ad7cfa7034d280459b2b2546288f247144 upstream. For PREEMPT enabled kernels the runtime instrumentation (RI) code contains a possible use-after-free bug. If a task that makes use of RI exits, it will execute do_exit() while still enabled for preemption. That function will call exit_thread_runtime_instr() via exit_thread(). If exit_thread_runtime_instr() gets preempted after the RI control block of the task has been freed but before the pointer to it is set to NULL, then save_ri_cb(), called from switch_to(), will write to already freed memory. Avoid this and simply disable preemption while freeing the control block and setting the pointer to NULL. Fixes: e4b8b3f33fca ("s390: add support for runtime instrumentation") Reviewed-by: Christian Borntraeger Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/kernel/runtime_instr.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/s390/kernel/runtime_instr.c +++ b/arch/s390/kernel/runtime_instr.c @@ -50,11 +50,13 @@ void exit_thread_runtime_instr(void) { struct task_struct *task = current; + preempt_disable(); if (!task->thread.ri_cb) return; disable_runtime_instr(); kfree(task->thread.ri_cb); task->thread.ri_cb = NULL; + preempt_enable(); } SYSCALL_DEFINE1(s390_runtime_instr, int, command) @@ -65,9 +67,7 @@ SYSCALL_DEFINE1(s390_runtime_instr, int, return -EOPNOTSUPP; if (command == S390_RUNTIME_INSTR_STOP) { - preempt_disable(); exit_thread_runtime_instr(); - preempt_enable(); return 0; }