[PATCH 2/2] PCI: lock each enable/disable num_vfs operation in sysfs

[Emil Tantilov]

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.

CC: Alexander Duyck <alexander.h.du...@intel.com>
Signed-off-by: Emil Tantilov <emil.s.tanti...@intel.com>
---
 drivers/pci/pci-sysfs.c |   24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 0666287..5b54cf5 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -472,7 +472,9 @@ 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;
 
        ret = kstrtou16(buf, 0, &num_vfs);
@@ -482,38 +484,46 @@ 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 = -EINVAL;
+               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;
 }