usb: cdc-wdm: close race between read and workqueue

wdm_read() cannot race with itself. However, in
service_outstanding_interrupt() it can race with the
workqueue, which can be triggered by error handling.

Hence we need to make sure that the WDM_RESPONDING
flag is not just only set but tested.

Fixes: afba937e540c9 ("USB: CDC WDM driver")
Cc: stable <stable@kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20240314115132.3907-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index c553decb5461078280b5f566a6ccd4035727c4a6..c8262e2f291778c785193b4311ab9613d0c18697 100644 (file)
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -485,6 +485,7 @@ out_free_mem:
 static int service_outstanding_interrupt(struct wdm_device *desc)
 {
        int rv = 0;
+       int used;
 
        /* submit read urb only if the device is waiting for it */
        if (!desc->resp_count || !--desc->resp_count)
@@ -499,7 +500,10 @@ static int service_outstanding_interrupt(struct wdm_device *desc)
                goto out;
        }
 
-       set_bit(WDM_RESPONDING, &desc->flags);
+       used = test_and_set_bit(WDM_RESPONDING, &desc->flags);
+       if (used)
+               goto out;
+
        spin_unlock_irq(&desc->iuspin);
        rv = usb_submit_urb(desc->response, GFP_KERNEL);
        spin_lock_irq(&desc->iuspin);