[PATCH 3.16 085/366] usb: gadget: function: printer: avoid spinlock recursion

Ben Hutchings
2018-11-11T20:15:35Z

From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

commit 9ada8c582088d32bd5c071c17213bc6edf37443a upstream.

If usb_gadget_giveback_request() is called in usb_ep_queue(),
this printer_write() is possible to cause spinlock recursion. So,
this patch adds spin_unlock() before calls usb_ep_queue() to avoid it.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/gadget/printer.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/drivers/usb/gadget/printer.c
+++ b/drivers/usb/gadget/printer.c
@@ -587,6 +587,7 @@ printer_write(struct file *fd, const cha
size_t size; /* Amount of data in a TX request. */
size_t bytes_copied = 0;
struct usb_request *req;
+ int value;

DBG(dev, "printer_write trying to send %d bytes\n", (int)len);

@@ -666,7 +667,11 @@ printer_write(struct file *fd, const cha
return -EAGAIN;
}

- if (usb_ep_queue(dev->in_ep, req, GFP_ATOMIC)) {
+ /* here, we unlock, and only unlock, to avoid deadlock. */
+ spin_unlock(&dev->lock);
+ value = usb_ep_queue(dev->in_ep, req, GFP_ATOMIC);
+ spin_lock(&dev->lock);
+ if (value) {
list_add(&req->list, &dev->tx_reqs);
spin_unlock_irqrestore(&dev->lock, flags);
mutex_unlock(&dev->lock_printer_io);