[PATCH 6.6 350/396] usb: cdc-wdm: close race between read and workqueue

Greg Kroah-Hartman
2024-04-01T16:53:47Z

From: Oliver Neukum <oneukum@suse.com>

commit 339f83612f3a569b194680768b22bf113c26a29d upstream.

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>
---
drivers/usb/class/cdc-wdm.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- 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
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);