linux-kernel - [PATCH] PCI: hv: Fix panic by calling hv_pci_remove

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Date:   Fri, 2 Aug 2019 01:32:28 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        Michael Kelley <mikelley@...rosoft.com>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "driverdev-devel@...uxdriverproject.org" 
        <driverdev-devel@...uxdriverproject.org>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        vkuznets <vkuznets@...hat.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        "jackm@...lanox.com" <jackm@...lanox.com>,
        Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH] PCI: hv: Fix panic by calling hv_pci_remove_slots() earlier


When a slot is removed, the pci_dev must still exist.

pci_remove_root_bus() removes and free all the pci_devs, so
hv_pci_remove_slots() must be called before pci_remove_root_bus(),
otherwise a general protection fault can happen, if the kernel is built
with the memory debugging options.

Fixes: 15becc2b56c6 ("PCI: hv: Add hv_pci_remove_slots() when we unload the driver")
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
Cc: stable@...r.kernel.org

---

When pci-hyperv is unloaded, this panic can happen:

 general protection fault:
 CPU: 2 PID: 1091 Comm: rmmod Not tainted 5.2.0+
 RIP: 0010:pci_slot_release+0x30/0xd0
 Call Trace:
  kobject_release+0x65/0x190
  pci_destroy_slot+0x25/0x60
  hv_pci_remove+0xec/0x110 [pci_hyperv]
  vmbus_remove+0x20/0x30 [hv_vmbus]
  device_release_driver_internal+0xd5/0x1b0
  driver_detach+0x44/0x7c
  bus_remove_driver+0x75/0xc7
  vmbus_driver_unregister+0x50/0xbd [hv_vmbus]
  __x64_sys_delete_module+0x136/0x200
  do_syscall_64+0x5e/0x220

 drivers/pci/controller/pci-hyperv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 6b9cc6e60a..68c611d 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2757,8 +2757,8 @@ static int hv_pci_remove(struct hv_device *hdev)
 		/* Remove the bus from PCI's point of view. */
 		pci_lock_rescan_remove();
 		pci_stop_root_bus(hbus->pci_bus);
-		pci_remove_root_bus(hbus->pci_bus);
 		hv_pci_remove_slots(hbus);
+		pci_remove_root_bus(hbus->pci_bus);
 		pci_unlock_rescan_remove();
 		hbus->state = hv_pcibus_removed;
 	}
-- 
1.8.3.1