From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61BDEC4363D for ; Tue, 6 Oct 2020 21:09:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3F4C208C7 for ; Tue, 6 Oct 2020 21:09:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727429AbgJFVJU (ORCPT ); Tue, 6 Oct 2020 17:09:20 -0400 Received: from mga11.intel.com ([192.55.52.93]:44603 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727370AbgJFVJT (ORCPT ); Tue, 6 Oct 2020 17:09:19 -0400 IronPort-SDR: n/3tjKO48euh3DFj3Ud65kNnd1apn2ftKVHolk6O3WcvtdzqbGbfZyuytuYbCKMgxMmRuz0/gn mkKhwvgXodRw== X-IronPort-AV: E=McAfee;i="6000,8403,9766"; a="161302110" X-IronPort-AV: E=Sophos;i="5.77,343,1596524400"; d="scan'208";a="161302110" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Oct 2020 14:09:19 -0700 IronPort-SDR: BCHtQym/6C62d0OCIBjOrffAsbQ2t6syJMdZIn/uhys/52Nz/LE3OhyP5MSerGUN9O5VFKLKYf iOMiYPLLDCWQ== X-IronPort-AV: E=Sophos;i="5.77,343,1596524400"; d="scan'208";a="527590603" Received: from agluck-desk2.sc.intel.com ([10.3.52.68]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Oct 2020 14:09:19 -0700 From: Tony Luck To: Borislav Petkov Cc: Tony Luck , Youquan Song , x86@kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 5/6] x86/mce: Recover from poison found while copying from user space Date: Tue, 6 Oct 2020 14:09:09 -0700 Message-Id: <20201006210910.21062-6-tony.luck@intel.com> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20201006210910.21062-1-tony.luck@intel.com> References: <20201005163130.GD21151@zn.tnic> <20201006210910.21062-1-tony.luck@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Existing kernel code can only recover from a machine check on code that is tagged in the exception table with a fault handling recovery path. Two new fields in the task structure to pass information from machine check handler to the "task_work" that is queued to run before the task returns to user mode: + mce_vaddr: will be initialized to the user virtual address of the fault in the case where the fault occurred in the kernel copying data from a user address. This is so that kill_me_maybe() can provide that information to the user SIGBUS handler. + mce_kflags: copy of the struct mce.kflags needed by kill_me_maybe() to determine if mce_vaddr is applicable to this error. Add code to recover from a machine check while copying data from user space to the kernel. Action for this case is the same as if the user touched the poison directly; unmap the page and send a SIGBUS to the task. Use a new helper function to share common code between the "fault in user mode" case and the "fault while copying from user" case. New code paths will be activated by the next patch which sets MCE_IN_KERNEL_COPYIN. Suggested-by: Borislav Petkov Signed-off-by: Tony Luck --- arch/x86/kernel/cpu/mce/core.c | 27 ++++++++++++++++++++------- include/linux/sched.h | 2 ++ 2 files changed, 22 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index 2d6caf09e8e6..5c423c4bab68 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -1260,6 +1260,21 @@ static void kill_me_maybe(struct callback_head *cb) kill_me_now(cb); } +static void queue_task_work(struct mce *m, int kill_it) +{ + current->mce_addr = m->addr; + current->mce_kflags = m->kflags; + current->mce_ripv = !!(m->mcgstatus & MCG_STATUS_RIPV); + current->mce_whole_page = whole_page(m); + + if (kill_it) + current->mce_kill_me.func = kill_me_now; + else + current->mce_kill_me.func = kill_me_maybe; + + task_work_add(current, ¤t->mce_kill_me, true); +} + /* * The actual machine check handler. This only handles real * exceptions when something got corrupted coming in through int 18. @@ -1401,13 +1416,8 @@ noinstr void do_machine_check(struct pt_regs *regs) /* If this triggers there is no way to recover. Die hard. */ BUG_ON(!on_thread_stack() || !user_mode(regs)); - current->mce_addr = m.addr; - current->mce_ripv = !!(m.mcgstatus & MCG_STATUS_RIPV); - current->mce_whole_page = whole_page(&m); - current->mce_kill_me.func = kill_me_maybe; - if (kill_it) - current->mce_kill_me.func = kill_me_now; - task_work_add(current, ¤t->mce_kill_me, true); + queue_task_work(&m, kill_it); + } else { /* * Handle an MCE which has happened in kernel space but from @@ -1422,6 +1432,9 @@ noinstr void do_machine_check(struct pt_regs *regs) if (!fixup_exception(regs, X86_TRAP_MC, 0, 0)) mce_panic("Failed kernel mode recovery", &m, msg); } + + if (m.kflags & MCE_IN_KERNEL_COPYIN) + queue_task_work(&m, kill_it); } out: mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); diff --git a/include/linux/sched.h b/include/linux/sched.h index 93ecd930efd3..2cbba3e2b150 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1308,6 +1308,8 @@ struct task_struct { #endif #ifdef CONFIG_X86_MCE + void __user *mce_vaddr; + __u64 mce_kflags; u64 mce_addr; __u64 mce_ripv : 1, mce_whole_page : 1, -- 2.21.1