cdc-acm: close race betrween suspend() and acm_softint

commit 0afccd7601514c4b83d8cc58c740089cc447051d upstream.

Suspend increments a counter, then kills the URBs,
then kills the scheduled work. The scheduled work, however,
may reschedule the URBs. Fix this by having the work
check the counter.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Cc: stable <stable@vger.kernel.org>
Tested-by: Jonas Karlsson <jonas.karlsson@actia.se>
Link: https://lore.kernel.org/r/20200415151358.32664-1-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 84d6f7d..4ef68e6 100644 (file)
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -557,14 +557,14 @@ static void acm_softint(struct work_struct *work)
        struct acm *acm = container_of(work, struct acm, work);
 
        if (test_bit(EVENT_RX_STALL, &acm->flags)) {
-               if (!(usb_autopm_get_interface(acm->data))) {
+               smp_mb(); /* against acm_suspend() */
+               if (!acm->susp_count) {
                        for (i = 0; i < acm->rx_buflimit; i++)
                                usb_kill_urb(acm->read_urbs[i]);
                        usb_clear_halt(acm->dev, acm->in);
                        acm_submit_read_urbs(acm, GFP_KERNEL);
-                       usb_autopm_put_interface(acm->data);
+                       clear_bit(EVENT_RX_STALL, &acm->flags);
                }
-               clear_bit(EVENT_RX_STALL, &acm->flags);
        }
 
        if (test_and_clear_bit(EVENT_TTY_WAKEUP, &acm->flags))