USB: gadget: f_hid: fix deadlock in f_hidg_write()

Radoslav Gerganov · Felipe Balbi · commit 072684e8c58d · 2019-03-20T10:58:48.000+02:00
In f_hidg_write() the write_spinlock is acquired before calling usb_ep_queue() which causes a deadlock when dummy_hcd is being used. This is because dummy_queue() callbacks into f_hidg_req_complete() which tries to acquire the same spinlock. This is (part of) the backtrace when the deadlock occurs: 0xffffffffc06b1410 in f_hidg_req_complete 0xffffffffc06a590a in usb_gadget_giveback_request 0xffffffffc06cfff2 in dummy_queue 0xffffffffc06a4b96 in usb_ep_queue 0xffffffffc06b1eb6 in f_hidg_write 0xffffffff8127730b in __vfs_write 0xffffffff812774d1 in vfs_write 0xffffffff81277725 in SYSC_write Fix this by releasing the write_spinlock before calling usb_ep_queue() Reviewed-by: James Bottomley <James.Bottomley@HansenPartnership.com> Tested-by: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: stable@vger.kernel.org # 4.11+ Fixes: 749494b ("usb: gadget: f_hid: fix: Move IN request allocation to set_alt()") Signed-off-by: Radoslav Gerganov <rgerganov@vmware.com> Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
@@ -391,20 +391,20 @@ static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
 	req->complete = f_hidg_req_complete;
 	req->context  = hidg;
 
+	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
+
 	status = usb_ep_queue(hidg->in_ep, req, GFP_ATOMIC);
 	if (status < 0) {
 		ERROR(hidg->func.config->cdev,
 			"usb_ep_queue error on int endpoint %zd\n", status);
-		goto release_write_pending_unlocked;
+		goto release_write_pending;
 	} else {
 		status = count;
 	}
-	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
 
 	return status;
 release_write_pending:
 	spin_lock_irqsave(&hidg->write_spinlock, flags);
-release_write_pending_unlocked:
 	hidg->write_pending = 0;
 	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
 
