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Subject[ 057/117] USB: cdc-wdm: cannot use dev_printk when device is gone
3.2-stable review patch.  If anyone has any objections, please let me know.

------------------
From: Bjørn Mork <bjorn@mork.no>

commit 6b0b79d38806481c1c8fffa7c5842f3c83679a42 upstream.

We cannot dereference a removed USB interface for
dev_printk. Use pr_debug instead where necessary.

Flush errors are expected if device is unplugged and are
therefore best ingored at this point.

Move the kill_urbs() call in wdm_release with dev_dbg()
for the non disconnect, as we know it has already been
called if WDM_DISCONNECTING is set. This does not
actually fix anything, but keeps the code more consistent.

Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/class/cdc-wdm.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -496,7 +496,9 @@
struct wdm_device *desc = file->private_data;

wait_event(desc->wait, !test_bit(WDM_IN_USE, &desc->flags));
- if (desc->werr < 0)
+
+ /* cannot dereference desc->intf if WDM_DISCONNECTING */
+ if (desc->werr < 0 && !test_bit(WDM_DISCONNECTING, &desc->flags))
dev_err(&desc->intf->dev, "Error in flush path: %d\n",
desc->werr);

@@ -586,12 +588,13 @@
mutex_unlock(&desc->wlock);

if (!desc->count) {
- dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
- kill_urbs(desc);
if (!test_bit(WDM_DISCONNECTING, &desc->flags)) {
+ dev_dbg(&desc->intf->dev, "wdm_release: cleanup");
+ kill_urbs(desc);
desc->intf->needs_remote_wakeup = 0;
} else {
- dev_dbg(&desc->intf->dev, "%s: device gone - cleaning up\n", __func__);
+ /* must avoid dev_printk here as desc->intf is invalid */
+ pr_debug(KBUILD_MODNAME " %s: device gone - cleaning up\n", __func__);
cleanup(desc);
}
}

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