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SubjectRe: [PATCH] rapidio: fix the missed put_device() for rio_mport_add_riodev
On Tue, Sep 22, 2020 at 03:25:25PM +0800, Jing Xiangfeng wrote:
> rio_mport_add_riodev() misses to call put_device() when the device
> already exists. Add the missed function call to fix it.
>

Looks good.

Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>

I notice that rio_mport_del_riodev() has a related bug.

1802 err = rio_add_device(rdev);
1803 if (err)
1804 goto cleanup;
1805 rio_dev_get(rdev);
^^^^^^^^^^^^^^^^^
This calls get_device(&rdev->dev);

1806
1807 return 0;
1808 cleanup:
1809 kfree(rdev);
1810 return err;
1811 }
1812
1813 static int rio_mport_del_riodev(struct mport_cdev_priv *priv, void __user *arg)
1814 {
1815 struct rio_rdev_info dev_info;
1816 struct rio_dev *rdev = NULL;
1817 struct device *dev;
1818 struct rio_mport *mport;
1819 struct rio_net *net;
1820
1821 if (copy_from_user(&dev_info, arg, sizeof(dev_info)))
1822 return -EFAULT;
1823 dev_info.name[sizeof(dev_info.name) - 1] = '\0';
1824
1825 mport = priv->md->mport;
1826
1827 /* If device name is specified, removal by name has priority */
1828 if (strlen(dev_info.name)) {
1829 dev = bus_find_device_by_name(&rio_bus_type, NULL,
1830 dev_info.name);
1831 if (dev)
1832 rdev = to_rio_dev(dev);

This path takes a second get_device(&rdev->dev);

1833 } else {
1834 do {
1835 rdev = rio_get_comptag(dev_info.comptag, rdev);
1836 if (rdev && rdev->dev.parent == &mport->net->dev &&
1837 rdev->destid == dev_info.destid &&
1838 rdev->hopcount == dev_info.hopcount)
1839 break;

This path does not call get_device().

1840 } while (rdev);
1841 }
1842
1843 if (!rdev) {
1844 rmcd_debug(RDEV,
1845 "device name:%s ct:0x%x did:0x%x hc:0x%x not found",
1846 dev_info.name, dev_info.comptag, dev_info.destid,
1847 dev_info.hopcount);
1848 return -ENODEV;
1849 }
1850
1851 net = rdev->net;
1852 rio_dev_put(rdev);

This drops a reference.

1853 rio_del_device(rdev, RIO_DEVICE_SHUTDOWN);

This drops a second reference. So presumably deleting by component tag
will lead to a use after free.

1854
1855 if (list_empty(&net->devices)) {
1856 rio_free_net(net);
1857 mport->net = NULL;
1858 }
1859
1860 return 0;
1861 }

regards,
dan carpenter

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