From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CB68A10973 for ; Mon, 26 Jun 2023 18:38:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E174AC433C8; Mon, 26 Jun 2023 18:38:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1687804719; bh=wn5mc2WIDyrRrHKdqV4mUbVfqA7ku+qD0hiLSx8oVmo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QMq7gNdkYCzku2DqQ2VRgB5EysN09S6WQPsLiLXlJNX7P4pf6Le80yyevCngv8Kf1 IlTckSj1mWRwEq/w3gpj1MDO64GDOIwYuS5DI72qxqaq3KuhJb18z+hc747sYmbhMJ dmW6/VXZog2Gl03jkQ3cc8eaz0M3+gZzE9Sh7KRE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dexuan Cui , Michael Kelley , Lorenzo Pieralisi , Wei Liu Subject: [PATCH 5.15 19/96] PCI: hv: Fix a race condition bug in hv_pci_query_relations() Date: Mon, 26 Jun 2023 20:11:34 +0200 Message-ID: <20230626180747.728251110@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230626180746.943455203@linuxfoundation.org> References: <20230626180746.943455203@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Dexuan Cui commit 440b5e3663271b0ffbd4908115044a6a51fb938b upstream. Since day 1 of the driver, there has been a race between hv_pci_query_relations() and survey_child_resources(): during fast device hotplug, hv_pci_query_relations() may error out due to device-remove and the stack variable 'comp' is no longer valid; however, pci_devices_present_work() -> survey_child_resources() -> complete() may be running on another CPU and accessing the no-longer-valid 'comp'. Fix the race by flushing the workqueue before we exit from hv_pci_query_relations(). Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs") Signed-off-by: Dexuan Cui Reviewed-by: Michael Kelley Acked-by: Lorenzo Pieralisi Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230615044451.5580-2-decui@microsoft.com Signed-off-by: Wei Liu Signed-off-by: Greg Kroah-Hartman --- drivers/pci/controller/pci-hyperv.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -2959,6 +2959,24 @@ static int hv_pci_query_relations(struct if (!ret) ret = wait_for_response(hdev, &comp); + /* + * In the case of fast device addition/removal, it's possible that + * vmbus_sendpacket() or wait_for_response() returns -ENODEV but we + * already got a PCI_BUS_RELATIONS* message from the host and the + * channel callback already scheduled a work to hbus->wq, which can be + * running pci_devices_present_work() -> survey_child_resources() -> + * complete(&hbus->survey_event), even after hv_pci_query_relations() + * exits and the stack variable 'comp' is no longer valid; as a result, + * a hang or a page fault may happen when the complete() calls + * raw_spin_lock_irqsave(). Flush hbus->wq before we exit from + * hv_pci_query_relations() to avoid the issues. Note: if 'ret' is + * -ENODEV, there can't be any more work item scheduled to hbus->wq + * after the flush_workqueue(): see vmbus_onoffer_rescind() -> + * vmbus_reset_channel_cb(), vmbus_rescind_cleanup() -> + * channel->rescind = true. + */ + flush_workqueue(hbus->wq); + return ret; }