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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 CCEB7C4320E for ; Mon, 16 Aug 2021 13:29:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B34AA60F46 for ; Mon, 16 Aug 2021 13:29:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241162AbhHPN3b (ORCPT ); Mon, 16 Aug 2021 09:29:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:44616 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239204AbhHPNSs (ORCPT ); Mon, 16 Aug 2021 09:18:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D293C61BE5; Mon, 16 Aug 2021 13:14:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1629119655; bh=JKylChIh2beEjyBH9CkfufBH+auVzM0uYJOtacwdIls=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0LUnqmqo43CCNcIzzpLMtyk9v4gmiMl9ZpP4rWHB5nrTbYVRTFCflYjjVB07wC6Vx i6CQCF3BcFchrE1+9OEXML+1BhdHzbivTQG/Z7Cu2W2MPhrNXJ5/qt2ou4Zbko8zRy w59J5y00GFkJfcGrSP3Pbu0DoU/GjsUwQQa0Ckso= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Maximilian Heyne , Boris Ostrovsky , Sasha Levin Subject: [PATCH 5.13 111/151] xen/events: Fix race in set_evtchn_to_irq Date: Mon, 16 Aug 2021 15:02:21 +0200 Message-Id: <20210816125447.715271387@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210816125444.082226187@linuxfoundation.org> References: <20210816125444.082226187@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Maximilian Heyne [ Upstream commit 88ca2521bd5b4e8b83743c01a2d4cb09325b51e9 ] There is a TOCTOU issue in set_evtchn_to_irq. Rows in the evtchn_to_irq mapping are lazily allocated in this function. The check whether the row is already present and the row initialization is not synchronized. Two threads can at the same time allocate a new row for evtchn_to_irq and add the irq mapping to the their newly allocated row. One thread will overwrite what the other has set for evtchn_to_irq[row] and therefore the irq mapping is lost. This will trigger a BUG_ON later in bind_evtchn_to_cpu: INFO: pci 0000:1a:15.4: [1d0f:8061] type 00 class 0x010802 INFO: nvme 0000:1a:12.1: enabling device (0000 -> 0002) INFO: nvme nvme77: 1/0/0 default/read/poll queues CRIT: kernel BUG at drivers/xen/events/events_base.c:427! WARN: invalid opcode: 0000 [#1] SMP NOPTI WARN: Workqueue: nvme-reset-wq nvme_reset_work [nvme] WARN: RIP: e030:bind_evtchn_to_cpu+0xc2/0xd0 WARN: Call Trace: WARN: set_affinity_irq+0x121/0x150 WARN: irq_do_set_affinity+0x37/0xe0 WARN: irq_setup_affinity+0xf6/0x170 WARN: irq_startup+0x64/0xe0 WARN: __setup_irq+0x69e/0x740 WARN: ? request_threaded_irq+0xad/0x160 WARN: request_threaded_irq+0xf5/0x160 WARN: ? nvme_timeout+0x2f0/0x2f0 [nvme] WARN: pci_request_irq+0xa9/0xf0 WARN: ? pci_alloc_irq_vectors_affinity+0xbb/0x130 WARN: queue_request_irq+0x4c/0x70 [nvme] WARN: nvme_reset_work+0x82d/0x1550 [nvme] WARN: ? check_preempt_wakeup+0x14f/0x230 WARN: ? check_preempt_curr+0x29/0x80 WARN: ? nvme_irq_check+0x30/0x30 [nvme] WARN: process_one_work+0x18e/0x3c0 WARN: worker_thread+0x30/0x3a0 WARN: ? process_one_work+0x3c0/0x3c0 WARN: kthread+0x113/0x130 WARN: ? kthread_park+0x90/0x90 WARN: ret_from_fork+0x3a/0x50 This patch sets evtchn_to_irq rows via a cmpxchg operation so that they will be set only once. The row is now cleared before writing it to evtchn_to_irq in order to not create a race once the row is visible for other threads. While at it, do not require the page to be zeroed, because it will be overwritten with -1's in clear_evtchn_to_irq_row anyway. Signed-off-by: Maximilian Heyne Fixes: d0b075ffeede ("xen/events: Refactor evtchn_to_irq array to be dynamically allocated") Link: https://lore.kernel.org/r/20210812130930.127134-1-mheyne@amazon.de Reviewed-by: Boris Ostrovsky Signed-off-by: Boris Ostrovsky Signed-off-by: Sasha Levin --- drivers/xen/events/events_base.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index d7e361fb0548..0e44098f3977 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -198,12 +198,12 @@ static void disable_dynirq(struct irq_data *data); static DEFINE_PER_CPU(unsigned int, irq_epoch); -static void clear_evtchn_to_irq_row(unsigned row) +static void clear_evtchn_to_irq_row(int *evtchn_row) { unsigned col; for (col = 0; col < EVTCHN_PER_ROW; col++) - WRITE_ONCE(evtchn_to_irq[row][col], -1); + WRITE_ONCE(evtchn_row[col], -1); } static void clear_evtchn_to_irq_all(void) @@ -213,7 +213,7 @@ static void clear_evtchn_to_irq_all(void) for (row = 0; row < EVTCHN_ROW(xen_evtchn_max_channels()); row++) { if (evtchn_to_irq[row] == NULL) continue; - clear_evtchn_to_irq_row(row); + clear_evtchn_to_irq_row(evtchn_to_irq[row]); } } @@ -221,6 +221,7 @@ static int set_evtchn_to_irq(evtchn_port_t evtchn, unsigned int irq) { unsigned row; unsigned col; + int *evtchn_row; if (evtchn >= xen_evtchn_max_channels()) return -EINVAL; @@ -233,11 +234,18 @@ static int set_evtchn_to_irq(evtchn_port_t evtchn, unsigned int irq) if (irq == -1) return 0; - evtchn_to_irq[row] = (int *)get_zeroed_page(GFP_KERNEL); - if (evtchn_to_irq[row] == NULL) + evtchn_row = (int *) __get_free_pages(GFP_KERNEL, 0); + if (evtchn_row == NULL) return -ENOMEM; - clear_evtchn_to_irq_row(row); + clear_evtchn_to_irq_row(evtchn_row); + + /* + * We've prepared an empty row for the mapping. If a different + * thread was faster inserting it, we can drop ours. + */ + if (cmpxchg(&evtchn_to_irq[row], NULL, evtchn_row) != NULL) + free_page((unsigned long) evtchn_row); } WRITE_ONCE(evtchn_to_irq[row][col], irq); -- 2.30.2