[PATCH 3.12 109/123] USB: usbfs: allow URBs to be reaped after disconnection

From: Jiri Slaby
Date: Tue Aug 04 2015 - 10:48:18 EST

From: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

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@xxxxxxxxxxxxxxxxxxx>
Tested-by: Chris Dickens <christopher.a.dickens@xxxxxxxxx>
Acked-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
drivers/usb/core/devio.c | 63 +++++++++++++++++++++++----------------
include/uapi/linux/usbdevice_fs.h | 3 +-
2 files changed, 39 insertions(+), 27 deletions(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index e69e408a39c9..c076050cab47 100644
--- 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;
}
@@ -1942,7 +1944,8 @@ 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)
@@ -2003,6 +2006,32 @@ 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;
@@ -2096,16 +2125,6 @@ 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));
@@ -2117,16 +2136,6 @@ 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);
@@ -2163,6 +2172,8 @@ 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 0c65e4b12617..ef29266ef77a 100644
--- 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 */

--
2.5.0

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