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")
Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
---
drivers/usb/class/cdc-wdm.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/class/cdc-wdm.c b/drivers/usb/class/cdc-wdm.c
index c553decb5461..c8262e2f2917 100644
--- a/drivers/usb/class/cdc-wdm.c
+++ b/drivers/usb/class/cdc-wdm.c
@@ -485,6 +485,7 @@ static ssize_t wdm_write
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);
--
2.44.0
