PCI: Fail new_id for vendor/device values already built into driver

While using the sysfs new_id interface, the user can unintentionally feed
incorrect values if the driver static table has a matching entry.  This is
possible since only the device and vendor fields are mandatory and the rest
are optional.  As a result, store_new_id() will fill in default values that
are then passed on to the driver and can have unintended consequences.

As an example, consider the ixgbe driver and the 82599EB network card:

  echo "8086 10fb" > /sys/bus/pci/drivers/ixgbe/new_id

This will pass a pci_device_id with driver_data = 0 to ixgbe_probe(), which
uses that zero to index a table of card operations.  The zeroth entry of
the table does *not* correspond to the 82599 operations.

This change returns an error if the user attempts to add a dynid for a
vendor/device combination for which a static entry already exists.
However, if the user intentionally wants a different set of values, she
must provide all the 7 fields and that will be accepted.

[bhelgaas: drop KVM text since the problem isn't KVM-specific]
Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 21 insertions, 1 deletions

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index d911e0c1f359..650ce8935fd7 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -107,7 +107,7 @@ store_new_id(struct device_driver *driver, const char *buf, size_t count)
                 subdevice=PCI_ANY_ID, class=0, class_mask=0;
         unsigned long driver_data=0;
         int fields=0;
-        int retval;
+        int retval = 0;
 
         fields = sscanf(buf, "%x %x %x %x %x %x %lx",
                         &vendor, &device, &subvendor, &subdevice,
@@ -115,6 +115,26 @@ store_new_id(struct device_driver *driver, const char *buf, size_t count)
         if (fields < 2)
                 return -EINVAL;
 
+        if (fields != 7) {
+                struct pci_dev *pdev = kzalloc(sizeof(*pdev), GFP_KERNEL);
+                if (!pdev)
+                        return -ENOMEM;
+
+                pdev->vendor = vendor;
+                pdev->device = device;
+                pdev->subsystem_vendor = subvendor;
+                pdev->subsystem_device = subdevice;
+                pdev->class = class;
+
+                if (pci_match_id(pdrv->id_table, pdev))
+                        retval = -EEXIST;
+
+                kfree(pdev);
+
+                if (retval)
+                        return retval;
+        }
+
         /* Only accept driver_data values that match an existing id_table
            entry */
         if (ids) {