USB: usbfs: allow URBs to be reaped after disconnection

commit 3f2cee73b650921b2e214bf487b2061a1c266504 upstream.

The usbfs API has a peculiar hole: Users are not allowed to reap their
URBs after the device has been disconnected.  There doesn't seem to be
any good reason for this; it is an ad-hoc inconsistency.

The patch allows users to issue the USBDEVFS_REAPURB and
USBDEVFS_REAPURBNDELAY ioctls (together with their 32-bit counterparts
on 64-bit systems) even after the device is gone.  If no URBs are
pending for a disconnected device then the ioctls will return -ENODEV
rather than -EAGAIN, because obviously no new URBs will ever be able
to complete.

The patch also adds a new capability flag for
USBDEVFS_GET_CAPABILITIES to indicate that the reap-after-disconnect
feature is supported.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Chris Dickens <christopher.a.dickens@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index 4c011cfb1da3d82dc09df978a01aae1b5a905db7..62e532fb82ad4a4230094becb2fa676a1a9b9d78 100644 (file)
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1593,7 +1593,7 @@ static struct async *reap_as(struct dev_state *ps)
        for (;;) {
                __set_current_state(TASK_INTERRUPTIBLE);
                as = async_getcompleted(ps);
-               if (as)
+               if (as || !connected(ps))
                        break;
                if (signal_pending(current))
                        break;
@@ -1616,7 +1616,7 @@ static int proc_reapurb(struct dev_state *ps, void __user *arg)
        }
        if (signal_pending(current))
                return -EINTR;
-       return -EIO;
+       return -ENODEV;
 }
 
 static int proc_reapurbnonblock(struct dev_state *ps, void __user *arg)
@@ -1625,10 +1625,11 @@ static int proc_reapurbnonblock(struct dev_state *ps, void __user *arg)
        struct async *as;
 
        as = async_getcompleted(ps);
-       retval = -EAGAIN;
        if (as) {
                retval = processcompl(as, (void __user * __user *)arg);
                free_async(as);
+       } else {
+               retval = (connected(ps) ? -EAGAIN : -ENODEV);
        }
        return retval;
 }
@@ -1758,7 +1759,7 @@ static int proc_reapurb_compat(struct dev_state *ps, void __user *arg)
        }
        if (signal_pending(current))
                return -EINTR;
-       return -EIO;
+       return -ENODEV;
 }
 
 static int proc_reapurbnonblock_compat(struct dev_state *ps, void __user *arg)
@@ -1766,11 +1767,12 @@ static int proc_reapurbnonblock_compat(struct dev_state *ps, void __user *arg)
        int retval;
        struct async *as;
 
-       retval = -EAGAIN;
        as = async_getcompleted(ps);
        if (as) {
                retval = processcompl_compat(as, (void __user * __user *)arg);
                free_async(as);
+       } else {
+               retval = (connected(ps) ? -EAGAIN : -ENODEV);
        }
        return retval;
 }
@@ -1941,7 +1943,8 @@ static int proc_get_capabilities(struct dev_state *ps, void __user *arg)
 {
        __u32 caps;
 
-       caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM;
+       caps = USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM |
+                       USBDEVFS_CAP_REAP_AFTER_DISCONNECT;
        if (!ps->dev->bus->no_stop_on_short)
                caps |= USBDEVFS_CAP_BULK_CONTINUATION;
        if (ps->dev->bus->sg_tablesize)
@@ -2002,6 +2005,32 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
                return -EPERM;
 
        usb_lock_device(dev);
+
+       /* Reap operations are allowed even after disconnection */
+       switch (cmd) {
+       case USBDEVFS_REAPURB:
+               snoop(&dev->dev, "%s: REAPURB\n", __func__);
+               ret = proc_reapurb(ps, p);
+               goto done;
+
+       case USBDEVFS_REAPURBNDELAY:
+               snoop(&dev->dev, "%s: REAPURBNDELAY\n", __func__);
+               ret = proc_reapurbnonblock(ps, p);
+               goto done;
+
+#ifdef CONFIG_COMPAT
+       case USBDEVFS_REAPURB32:
+               snoop(&dev->dev, "%s: REAPURB32\n", __func__);
+               ret = proc_reapurb_compat(ps, p);
+               goto done;
+
+       case USBDEVFS_REAPURBNDELAY32:
+               snoop(&dev->dev, "%s: REAPURBNDELAY32\n", __func__);
+               ret = proc_reapurbnonblock_compat(ps, p);
+               goto done;
+#endif
+       }
+
        if (!connected(ps)) {
                usb_unlock_device(dev);
                return -ENODEV;
@@ -2095,16 +2124,6 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
                        inode->i_mtime = CURRENT_TIME;
                break;
 
-       case USBDEVFS_REAPURB32:
-               snoop(&dev->dev, "%s: REAPURB32\n", __func__);
-               ret = proc_reapurb_compat(ps, p);
-               break;
-
-       case USBDEVFS_REAPURBNDELAY32:
-               snoop(&dev->dev, "%s: REAPURBNDELAY32\n", __func__);
-               ret = proc_reapurbnonblock_compat(ps, p);
-               break;
-
        case USBDEVFS_IOCTL32:
                snoop(&dev->dev, "%s: IOCTL32\n", __func__);
                ret = proc_ioctl_compat(ps, ptr_to_compat(p));
@@ -2116,16 +2135,6 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
                ret = proc_unlinkurb(ps, p);
                break;
 
-       case USBDEVFS_REAPURB:
-               snoop(&dev->dev, "%s: REAPURB\n", __func__);
-               ret = proc_reapurb(ps, p);
-               break;
-
-       case USBDEVFS_REAPURBNDELAY:
-               snoop(&dev->dev, "%s: REAPURBNDELAY\n", __func__);
-               ret = proc_reapurbnonblock(ps, p);
-               break;
-
        case USBDEVFS_DISCSIGNAL:
                snoop(&dev->dev, "%s: DISCSIGNAL\n", __func__);
                ret = proc_disconnectsignal(ps, p);
@@ -2162,6 +2171,8 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
                ret = proc_disconnect_claim(ps, p);
                break;
        }
+
+ done:
        usb_unlock_device(dev);
        if (ret >= 0)
                inode->i_atime = CURRENT_TIME;

diff --git a/include/uapi/linux/usbdevice_fs.h b/include/uapi/linux/usbdevice_fs.h
index 0c65e4b1261717f71b7bdeef94da72b608eec392..ef29266ef77a17fb8bb7ef522fd6c20aaccfc020 100644 (file)
--- a/include/uapi/linux/usbdevice_fs.h
+++ b/include/uapi/linux/usbdevice_fs.h
@@ -125,11 +125,12 @@ struct usbdevfs_hub_portinfo {
        char port [127];        /* e.g. port 3 connects to device 27 */
 };
 
-/* Device capability flags */
+/* System and bus capability flags */
 #define USBDEVFS_CAP_ZERO_PACKET               0x01
 #define USBDEVFS_CAP_BULK_CONTINUATION         0x02
 #define USBDEVFS_CAP_NO_PACKET_SIZE_LIM                0x04
 #define USBDEVFS_CAP_BULK_SCATTER_GATHER       0x08
+#define USBDEVFS_CAP_REAP_AFTER_DISCONNECT     0x10
 
 /* USBDEVFS_DISCONNECT_CLAIM flags & struct */