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USB: usbfs: allow URBs to be reaped after disconnection
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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 <greg@kroah.com>
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@AlanStern @gregkh
AlanStern authored and gregkh committed Jan 31, 2015
1 parent 17136d4 commit 3f2cee7
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Showing 2 changed files with 39 additions and 27 deletions.
63 changes: 37 additions & 26 deletions drivers/usb/core/devio.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1689,7 +1689,7 @@ static struct async *reap_as(struct usb_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;
Expand All @@ -1712,7 +1712,7 @@ static int proc_reapurb(struct usb_dev_state *ps, void __user *arg)
}
if (signal_pending(current))
return -EINTR;
return -EIO;
return -ENODEV;
}

static int proc_reapurbnonblock(struct usb_dev_state *ps, void __user *arg)
Expand All @@ -1721,10 +1721,11 @@ static int proc_reapurbnonblock(struct usb_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;
}
Expand Down Expand Up @@ -1854,19 +1855,20 @@ static int proc_reapurb_compat(struct usb_dev_state *ps, void __user *arg)
}
if (signal_pending(current))
return -EINTR;
return -EIO;
return -ENODEV;
}

static int proc_reapurbnonblock_compat(struct usb_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;
}
Expand Down Expand Up @@ -2038,7 +2040,8 @@ static int proc_get_capabilities(struct usb_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)
Expand Down Expand Up @@ -2138,6 +2141,32 @@ 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;
Expand Down Expand Up @@ -2231,16 +2260,6 @@ 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));
Expand All @@ -2252,16 +2271,6 @@ 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);
Expand Down Expand Up @@ -2304,6 +2313,8 @@ static long usbdev_do_ioctl(struct file *file, unsigned int cmd,
ret = proc_free_streams(ps, p);
break;
}

done:
usb_unlock_device(dev);
if (ret >= 0)
inode->i_atime = CURRENT_TIME;
Expand Down
3 changes: 2 additions & 1 deletion include/uapi/linux/usbdevice_fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -128,11 +128,12 @@ 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 */

Expand Down

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