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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4AD4C46467 for ; Mon, 23 May 2022 17:58:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244228AbiEWR6C (ORCPT ); Mon, 23 May 2022 13:58:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37312 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241420AbiEWRao (ORCPT ); Mon, 23 May 2022 13:30:44 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5FD8E4E3AB; Mon, 23 May 2022 10:26:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8B46A60B35; Mon, 23 May 2022 17:26:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8EA4CC385AA; Mon, 23 May 2022 17:26:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1653326787; bh=tcHeGnF2PoJIpurfi0R4moFcTJ05kj7019N3a7rLRAE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Nzsc2Ui8yiTM9GvBCODo5wfdtCeeluP9bnQmlUa0w6k9XYHrO8TwRpmjD2ihoBoal +/alzksKesjzXSoEWs0q4bu9mvOd5r/kE10jDHj4Cib0WmfRl8ANIj9SCezpVKLYVF KqGAlwiHQeU4F0Y22/pPmOqA50Fns0qnrIahAzAg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Will Deacon , Prakruthi Deepak Heragu , Elliot Berman , "Srivatsa S. Bhat (VMware)" Subject: [PATCH 5.17 058/158] arm64: paravirt: Use RCU read locks to guard stolen_time Date: Mon, 23 May 2022 19:03:35 +0200 Message-Id: <20220523165840.433023993@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220523165830.581652127@linuxfoundation.org> References: <20220523165830.581652127@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: Prakruthi Deepak Heragu commit 19bef63f951e47dd4ba54810e6f7c7ff9344a3ef upstream. During hotplug, the stolen time data structure is unmapped and memset. There is a possibility of the timer IRQ being triggered before memset and stolen time is getting updated as part of this timer IRQ handler. This causes the below crash in timer handler - [ 3457.473139][ C5] Unable to handle kernel paging request at virtual address ffffffc03df05148 ... [ 3458.154398][ C5] Call trace: [ 3458.157648][ C5] para_steal_clock+0x30/0x50 [ 3458.162319][ C5] irqtime_account_process_tick+0x30/0x194 [ 3458.168148][ C5] account_process_tick+0x3c/0x280 [ 3458.173274][ C5] update_process_times+0x5c/0xf4 [ 3458.178311][ C5] tick_sched_timer+0x180/0x384 [ 3458.183164][ C5] __run_hrtimer+0x160/0x57c [ 3458.187744][ C5] hrtimer_interrupt+0x258/0x684 [ 3458.192698][ C5] arch_timer_handler_virt+0x5c/0xa0 [ 3458.198002][ C5] handle_percpu_devid_irq+0xdc/0x414 [ 3458.203385][ C5] handle_domain_irq+0xa8/0x168 [ 3458.208241][ C5] gic_handle_irq.34493+0x54/0x244 [ 3458.213359][ C5] call_on_irq_stack+0x40/0x70 [ 3458.218125][ C5] do_interrupt_handler+0x60/0x9c [ 3458.223156][ C5] el1_interrupt+0x34/0x64 [ 3458.227560][ C5] el1h_64_irq_handler+0x1c/0x2c [ 3458.232503][ C5] el1h_64_irq+0x7c/0x80 [ 3458.236736][ C5] free_vmap_area_noflush+0x108/0x39c [ 3458.242126][ C5] remove_vm_area+0xbc/0x118 [ 3458.246714][ C5] vm_remove_mappings+0x48/0x2a4 [ 3458.251656][ C5] __vunmap+0x154/0x278 [ 3458.255796][ C5] stolen_time_cpu_down_prepare+0xc0/0xd8 [ 3458.261542][ C5] cpuhp_invoke_callback+0x248/0xc34 [ 3458.266842][ C5] cpuhp_thread_fun+0x1c4/0x248 [ 3458.271696][ C5] smpboot_thread_fn+0x1b0/0x400 [ 3458.276638][ C5] kthread+0x17c/0x1e0 [ 3458.280691][ C5] ret_from_fork+0x10/0x20 As a fix, introduce rcu lock to update stolen time structure. Fixes: 75df529bec91 ("arm64: paravirt: Initialize steal time when cpu is online") Cc: stable@vger.kernel.org Suggested-by: Will Deacon Signed-off-by: Prakruthi Deepak Heragu Signed-off-by: Elliot Berman Reviewed-by: Srivatsa S. Bhat (VMware) Link: https://lore.kernel.org/r/20220513174654.362169-1-quic_eberman@quicinc.com Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/paravirt.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) --- a/arch/arm64/kernel/paravirt.c +++ b/arch/arm64/kernel/paravirt.c @@ -35,7 +35,7 @@ static u64 native_steal_clock(int cpu) DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock); struct pv_time_stolen_time_region { - struct pvclock_vcpu_stolen_time *kaddr; + struct pvclock_vcpu_stolen_time __rcu *kaddr; }; static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region); @@ -52,7 +52,9 @@ early_param("no-steal-acc", parse_no_ste /* return stolen time in ns by asking the hypervisor */ static u64 para_steal_clock(int cpu) { + struct pvclock_vcpu_stolen_time *kaddr = NULL; struct pv_time_stolen_time_region *reg; + u64 ret = 0; reg = per_cpu_ptr(&stolen_time_region, cpu); @@ -61,28 +63,37 @@ static u64 para_steal_clock(int cpu) * online notification callback runs. Until the callback * has run we just return zero. */ - if (!reg->kaddr) + rcu_read_lock(); + kaddr = rcu_dereference(reg->kaddr); + if (!kaddr) { + rcu_read_unlock(); return 0; + } - return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time)); + ret = le64_to_cpu(READ_ONCE(kaddr->stolen_time)); + rcu_read_unlock(); + return ret; } static int stolen_time_cpu_down_prepare(unsigned int cpu) { + struct pvclock_vcpu_stolen_time *kaddr = NULL; struct pv_time_stolen_time_region *reg; reg = this_cpu_ptr(&stolen_time_region); if (!reg->kaddr) return 0; - memunmap(reg->kaddr); - memset(reg, 0, sizeof(*reg)); + kaddr = rcu_replace_pointer(reg->kaddr, NULL, true); + synchronize_rcu(); + memunmap(kaddr); return 0; } static int stolen_time_cpu_online(unsigned int cpu) { + struct pvclock_vcpu_stolen_time *kaddr = NULL; struct pv_time_stolen_time_region *reg; struct arm_smccc_res res; @@ -93,17 +104,19 @@ static int stolen_time_cpu_online(unsign if (res.a0 == SMCCC_RET_NOT_SUPPORTED) return -EINVAL; - reg->kaddr = memremap(res.a0, + kaddr = memremap(res.a0, sizeof(struct pvclock_vcpu_stolen_time), MEMREMAP_WB); + rcu_assign_pointer(reg->kaddr, kaddr); + if (!reg->kaddr) { pr_warn("Failed to map stolen time data structure\n"); return -ENOMEM; } - if (le32_to_cpu(reg->kaddr->revision) != 0 || - le32_to_cpu(reg->kaddr->attributes) != 0) { + if (le32_to_cpu(kaddr->revision) != 0 || + le32_to_cpu(kaddr->attributes) != 0) { pr_warn_once("Unexpected revision or attributes in stolen time data\n"); return -ENXIO; }