PCI: Lock each enable/disable num_vfs operation in sysfs

Enabling/disabling SRIOV via sysfs by echo-ing multiple values
simultaneously:

  # echo 63 > /sys/class/net/ethX/device/sriov_numvfs&
  # echo 63 > /sys/class/net/ethX/device/sriov_numvfs

  # sleep 5

  # echo 0 > /sys/class/net/ethX/device/sriov_numvfs&
  # echo 0 > /sys/class/net/ethX/device/sriov_numvfs

results in the following bug:

  kernel BUG at drivers/pci/iov.c:495!
  invalid opcode: 0000 [#1] SMP
  CPU: 1 PID: 8050 Comm: bash Tainted: G   W   4.9.0-rc7-net-next #2092
  RIP: 0010:[<ffffffff813b1647>]
	    [<ffffffff813b1647>] pci_iov_release+0x57/0x60

  Call Trace:
   [<ffffffff81391726>] pci_release_dev+0x26/0x70
   [<ffffffff8155be6e>] device_release+0x3e/0xb0
   [<ffffffff81365ee7>] kobject_cleanup+0x67/0x180
   [<ffffffff81365d9d>] kobject_put+0x2d/0x60
   [<ffffffff8155bc27>] put_device+0x17/0x20
   [<ffffffff8139c08a>] pci_dev_put+0x1a/0x20
   [<ffffffff8139cb6b>] pci_get_dev_by_id+0x5b/0x90
   [<ffffffff8139cca5>] pci_get_subsys+0x35/0x40
   [<ffffffff8139ccc8>] pci_get_device+0x18/0x20
   [<ffffffff8139ccfb>] pci_get_domain_bus_and_slot+0x2b/0x60
   [<ffffffff813b09e7>] pci_iov_remove_virtfn+0x57/0x180
   [<ffffffff813b0b95>] pci_disable_sriov+0x65/0x140
   [<ffffffffa00a1af7>] ixgbe_disable_sriov+0xc7/0x1d0 [ixgbe]
   [<ffffffffa00a1e9d>] ixgbe_pci_sriov_configure+0x3d/0x170 [ixgbe]
   [<ffffffff8139d28c>] sriov_numvfs_store+0xdc/0x130
  ...
  RIP  [<ffffffff813b1647>] pci_iov_release+0x57/0x60

Use the existing mutex lock to protect each enable/disable operation.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
CC: Alexander Duyck <alexander.h.duyck@intel.com>

1 files changed, 16 insertions, 7 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 0666287..25d010d 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -472,6 +472,7 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 				  const char *buf, size_t count)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
+	struct pci_sriov *iov = pdev->sriov;
 	int ret;
 	u16 num_vfs;
 
@@ -482,38 +483,46 @@ static ssize_t sriov_numvfs_store(struct device *dev,
 	if (num_vfs > pci_sriov_get_totalvfs(pdev))
 		return -ERANGE;
 
+	mutex_lock(&iov->dev->sriov->lock);
+
 	if (num_vfs == pdev->sriov->num_VFs)
-		return count;		/* no change */
+		goto exit;
 
 	/* is PF driver loaded w/callback */
 	if (!pdev->driver || !pdev->driver->sriov_configure) {
 		dev_info(&pdev->dev, "Driver doesn't support SRIOV configuration via sysfs\n");
-		return -ENOSYS;
+		ret = -ENOENT;
+		goto exit;
 	}
 
 	if (num_vfs == 0) {
 		/* disable VFs */
 		ret = pdev->driver->sriov_configure(pdev, 0);
-		if (ret < 0)
-			return ret;
-		return count;
+		goto exit;
 	}
 
 	/* enable VFs */
 	if (pdev->sriov->num_VFs) {
 		dev_warn(&pdev->dev, "%d VFs already enabled. Disable before enabling %d VFs\n",
 			 pdev->sriov->num_VFs, num_vfs);
-		return -EBUSY;
+		ret = -EBUSY;
+		goto exit;
 	}
 
 	ret = pdev->driver->sriov_configure(pdev, num_vfs);
 	if (ret < 0)
-		return ret;
+		goto exit;
 
 	if (ret != num_vfs)
 		dev_warn(&pdev->dev, "%d VFs requested; only %d enabled\n",
 			 num_vfs, ret);
 
+exit:
+	mutex_unlock(&iov->dev->sriov->lock);
+
+	if (ret < 0)
+		return ret;
+
 	return count;
 }