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Commit 59044112 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
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usb: cdc-wdm: close race between read and workqueue 



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: afba937e ("USB: CDC WDM driver")
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarOliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20240314115132.3907-1-oneukum@suse.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3a679f8a

drivers/usb/class/cdc-wdm.c

+5 −1
Original line number Diff line number Diff line
@@ -471,6 +471,7 @@ 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)
@@ -485,7 +486,10 @@ 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);