From patchwork Mon Jan 11 21:44:50 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Luck X-Patchwork-Id: 12011681 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 81956C433E0 for ; Mon, 11 Jan 2021 21:46:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EF7522CB2 for ; Mon, 11 Jan 2021 21:46:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731292AbhAKVqF (ORCPT ); Mon, 11 Jan 2021 16:46:05 -0500 Received: from mga14.intel.com ([192.55.52.115]:20892 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731682AbhAKVqE (ORCPT ); Mon, 11 Jan 2021 16:46:04 -0500 IronPort-SDR: PIdsy3Zxk0jwQ23aW2KsWnxbcjjzxyJYh1AoDJ1fORsXh+oDsGWa+APuLor2nUytnjlNDzzgvd e/AUCF+2cWNw== X-IronPort-AV: E=McAfee;i="6000,8403,9861"; a="177166209" X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="177166209" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -0800 IronPort-SDR: /EYgtN6RyiajNarZm1QuziXZRJmrrwZcrPFB6ZrKQDG+4v0wQOeZWxJaoRULpM/ZF8lHay2iho V+jp2RHT8YtA== X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="352760865" Received: from agluck-desk2.sc.intel.com ([10.3.52.68]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -0800 From: Tony Luck To: Borislav Petkov Cc: Tony Luck , x86@kernel.org, Andrew Morton , Peter Zijlstra , Darren Hart , Andy Lutomirski , linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery Date: Mon, 11 Jan 2021 13:44:50 -0800 Message-Id: <20210111214452.1826-2-tony.luck@intel.com> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20210111214452.1826-1-tony.luck@intel.com> References: <20210108222251.14391-1-tony.luck@intel.com> <20210111214452.1826-1-tony.luck@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org Recovery action when get_user() triggers a machine check uses the fixup path to make get_user() return -EFAULT. Also queue_task_work() sets up so that kill_me_maybe() will be called on return to user mode to send a SIGBUS to the current process. But there are places in the kernel where the code assumes that this EFAULT return was simply because of a page fault. The code takes some action to fix that, and then retries the access. This results in a second machine check. While processing this second machine check queue_task_work() is called again. But since this uses the same callback_head structure that was used in the first call, the net result is an entry on the current->task_works list that points to itself. When task_work_run() is called it loops forever in this code: do { next = work->next; work->func(work); work = next; cond_resched(); } while (work); Add a "mce_busy" flag bit to detect this situation and panic when it happens. Signed-off-by: Tony Luck --- arch/x86/kernel/cpu/mce/core.c | 7 ++++++- include/linux/sched.h | 3 ++- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c index 13d3f1cbda17..1bf11213e093 100644 --- a/arch/x86/kernel/cpu/mce/core.c +++ b/arch/x86/kernel/cpu/mce/core.c @@ -1246,6 +1246,7 @@ static void kill_me_maybe(struct callback_head *cb) struct task_struct *p = container_of(cb, struct task_struct, mce_kill_me); int flags = MF_ACTION_REQUIRED; + p->mce_busy = 0; pr_err("Uncorrected hardware memory error in user-access at %llx", p->mce_addr); if (!p->mce_ripv) @@ -1268,6 +1269,7 @@ static void kill_me_maybe(struct callback_head *cb) static void queue_task_work(struct mce *m, int kill_current_task) { + current->mce_busy = 1; current->mce_addr = m->addr; current->mce_kflags = m->kflags; current->mce_ripv = !!(m->mcgstatus & MCG_STATUS_RIPV); @@ -1431,8 +1433,11 @@ noinstr void do_machine_check(struct pt_regs *regs) mce_panic("Failed kernel mode recovery", &m, msg); } - if (m.kflags & MCE_IN_KERNEL_COPYIN) + if (m.kflags & MCE_IN_KERNEL_COPYIN) { + if (current->mce_busy) + mce_panic("Multiple copyin", &m, msg); queue_task_work(&m, kill_current_task); + } } out: mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); diff --git a/include/linux/sched.h b/include/linux/sched.h index 6e3a5eeec509..a763a76eac57 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1360,7 +1360,8 @@ struct task_struct { u64 mce_addr; __u64 mce_ripv : 1, mce_whole_page : 1, - __mce_reserved : 62; + mce_busy : 1, + __mce_reserved : 61; struct callback_head mce_kill_me; #endif From patchwork Mon Jan 11 21:44:51 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Luck X-Patchwork-Id: 12011683 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 3C7FAC433DB for ; Mon, 11 Jan 2021 21:46:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 012D122CB8 for ; Mon, 11 Jan 2021 21:46:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731682AbhAKVqU (ORCPT ); Mon, 11 Jan 2021 16:46:20 -0500 Received: from mga14.intel.com ([192.55.52.115]:20892 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731244AbhAKVqU (ORCPT ); Mon, 11 Jan 2021 16:46:20 -0500 IronPort-SDR: SX9KRNCcOaCwHv2YBWGvMQP2KuzFy6EBTk+2zKJdemiIurw0jmzmRz6dnpZYe3BBTE4beRiTcU W4s9/9iwIm9A== X-IronPort-AV: E=McAfee;i="6000,8403,9861"; a="177166210" X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="177166210" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -0800 IronPort-SDR: X4mXz3V4ZwtebLI/yZy2KXfk+qBWTED9qqdPXsjYD5tqRiH2UoJ4SxqZD1LZhzSpKaqg9IWTRL 4b6bbRJwj8pw== X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="352760868" Received: from agluck-desk2.sc.intel.com ([10.3.52.68]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -0800 From: Tony Luck To: Borislav Petkov Cc: Tony Luck , x86@kernel.org, Andrew Morton , Peter Zijlstra , Darren Hart , Andy Lutomirski , linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 2/3] x86/mce: Add new return value to get_user() for machine check Date: Mon, 11 Jan 2021 13:44:51 -0800 Message-Id: <20210111214452.1826-3-tony.luck@intel.com> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20210111214452.1826-1-tony.luck@intel.com> References: <20210108222251.14391-1-tony.luck@intel.com> <20210111214452.1826-1-tony.luck@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org When an exception occurs during any of the get_user() functions fixup_exception() passes the trap number of the exception in regs->ax to the fixup code. Check for X86_TRAP_MC and return -ENXIO ("No such device or address") so that callers can take action to avoid repeating an access to an address that has an uncorrectable error. Signed-off-by: Tony Luck --- arch/x86/lib/getuser.S | 8 +++++++- arch/x86/mm/extable.c | 1 + 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S index fa1bc2104b32..c49a449fced6 100644 --- a/arch/x86/lib/getuser.S +++ b/arch/x86/lib/getuser.S @@ -17,7 +17,7 @@ * * Inputs: %[r|e]ax contains the address. * - * Outputs: %[r|e]ax is error code (0 or -EFAULT) + * Outputs: %[r|e]ax is error code (0 or -EFAULT or -ENXIO) * %[r|e]dx contains zero-extended value * %ecx contains the high half for 32-bit __get_user_8 * @@ -34,6 +34,7 @@ #include #include #include +#include #define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RDTSC @@ -168,8 +169,13 @@ SYM_CODE_START_LOCAL(.Lbad_get_user_clac) ASM_CLAC bad_get_user: xor %edx,%edx + cmpl $X86_TRAP_MC,%eax + je mce_get_user mov $(-EFAULT),%_ASM_AX ret +mce_get_user: + mov $(-ENXIO),%_ASM_AX + ret SYM_CODE_END(.Lbad_get_user_clac) #ifdef CONFIG_X86_32 diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c index b93d6cd08a7f..ac4fcb820c40 100644 --- a/arch/x86/mm/extable.c +++ b/arch/x86/mm/extable.c @@ -77,6 +77,7 @@ __visible bool ex_handler_uaccess(const struct exception_table_entry *fixup, { WARN_ONCE(trapnr == X86_TRAP_GP, "General protection fault in user access. Non-canonical address?"); regs->ip = ex_fixup_addr(fixup); + regs->ax = trapnr; return true; } EXPORT_SYMBOL(ex_handler_uaccess); From patchwork Mon Jan 11 21:44:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tony Luck X-Patchwork-Id: 12011685 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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 12687C433DB for ; Mon, 11 Jan 2021 21:46:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C804122CB2 for ; Mon, 11 Jan 2021 21:46:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731408AbhAKVqa (ORCPT ); Mon, 11 Jan 2021 16:46:30 -0500 Received: from mga14.intel.com ([192.55.52.115]:20926 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731135AbhAKVq3 (ORCPT ); Mon, 11 Jan 2021 16:46:29 -0500 IronPort-SDR: +2t+Mdtmtl6g2dk7YF2UYUJ8jJN6w4gl6ZCntod3VCageBFm0FUumbmb2OfQQLVaqgHVaW7slc Qzpqh8swNDAA== X-IronPort-AV: E=McAfee;i="6000,8403,9861"; a="177166211" X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="177166211" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -0800 IronPort-SDR: +hZpGNm/k1XCMrPo4g89/aNf7U2+ZmNAXdUEFb5sHxdr4/ePzBAjecP6x/wx3X/nPg3xc+P4vb GyWVQYoOAztw== X-IronPort-AV: E=Sophos;i="5.79,339,1602572400"; d="scan'208";a="352760874" Received: from agluck-desk2.sc.intel.com ([10.3.52.68]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2021 13:45:08 -0800 From: Tony Luck To: Borislav Petkov Cc: Tony Luck , x86@kernel.org, Andrew Morton , Peter Zijlstra , Darren Hart , Andy Lutomirski , linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v2 3/3] futex, x86/mce: Avoid double machine checks Date: Mon, 11 Jan 2021 13:44:52 -0800 Message-Id: <20210111214452.1826-4-tony.luck@intel.com> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20210111214452.1826-1-tony.luck@intel.com> References: <20210108222251.14391-1-tony.luck@intel.com> <20210111214452.1826-1-tony.luck@intel.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-edac@vger.kernel.org futex_wait_setup() first tries to read the user value with page faults disabled (because it holds a lock, and so cannot sleep). If that read fails it drops the lock and tries again. But there are now two reasons why the user space read can fail. Either: 1) legacy case of a page fault, in which case it is reasonable to retry 2) machine check on the user address, bad idea to re-read Check for the ENXIO return code from the first get_user() call and immediately return an error without re-reading the futex. Signed-off-by: Tony Luck --- kernel/futex.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index c47d1015d759..b11166712a9f 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -723,7 +723,7 @@ static int get_futex_value_locked(u32 *dest, u32 __user *from) ret = __get_user(*dest, from); pagefault_enable(); - return ret ? -EFAULT : 0; + return (ret == -ENXIO) ? ret : ret ? -EFAULT : 0; } @@ -2658,6 +2658,9 @@ static int futex_wait_setup(u32 __user *uaddr, u32 val, unsigned int flags, if (ret) { queue_unlock(*hb); + if (ret == -ENXIO) + return ret; + ret = get_user(uval, uaddr); if (ret) return ret;