This is a note to let you know that I've just added the patch titled USB: CDC-ACM: fix poison/unpoison imbalance to the 5.12-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: usb-cdc-acm-fix-poison-unpoison-imbalance.patch and it can be found in the queue-5.12 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From a8b3b519618f30a87a304c4e120267ce6f8dc68a Mon Sep 17 00:00:00 2001 From: Oliver Neukum <oneukum@xxxxxxxx> Date: Wed, 21 Apr 2021 09:45:13 +0200 Subject: USB: CDC-ACM: fix poison/unpoison imbalance From: Oliver Neukum <oneukum@xxxxxxxx> commit a8b3b519618f30a87a304c4e120267ce6f8dc68a upstream. suspend() does its poisoning conditionally, resume() does it unconditionally. On a device with combined interfaces this will balance, on a device with two interfaces the counter will go negative and resubmission will fail. Both actions need to be done conditionally. Fixes: 6069e3e927c8f ("USB: cdc-acm: untangle a circular dependency between callback and softint") Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20210421074513.4327-1-oneukum@xxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/usb/class/cdc-acm.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1634,12 +1634,13 @@ static int acm_resume(struct usb_interfa struct urb *urb; int rv = 0; - acm_unpoison_urbs(acm); spin_lock_irq(&acm->write_lock); if (--acm->susp_count) goto out; + acm_unpoison_urbs(acm); + if (tty_port_initialized(&acm->port)) { rv = usb_submit_urb(acm->ctrlurb, GFP_ATOMIC); Patches currently in stable-queue which might be from oneukum@xxxxxxxx are queue-5.12/usb-cdc-acm-fix-poison-unpoison-imbalance.patch