From: Johan Hovold johan@kernel.org
commit 65a205e6113506e69a503b61d97efec43fc10fd7 upstream.
A recent change that started reporting break events to the line discipline caused the tty-buffer insertions to no longer be serialised by inserting events also from the completion handler for the interrupt endpoint.
Completion calls for distinct endpoints are not guaranteed to be serialised. For example, in case a host-controller driver uses bottom-half completion, the interrupt and bulk-in completion handlers can end up running in parallel on two CPUs (high-and low-prio tasklets, respectively) thereby breaking the tty layer's single producer assumption.
Fix this by holding the read lock also when inserting characters from the bulk endpoint.
Fixes: 08dff274edda ("cdc-acm: fix BREAK rx code path adding necessary calls") Cc: stable@vger.kernel.org Acked-by: Oliver Neukum oneukum@suse.com Signed-off-by: Johan Hovold johan@kernel.org Link: https://lore.kernel.org/r/20210929090937.7410-2-johan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/class/cdc-acm.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -475,11 +475,16 @@ static int acm_submit_read_urbs(struct a
static void acm_process_read_urb(struct acm *acm, struct urb *urb) { + unsigned long flags; + if (!urb->actual_length) return;
+ spin_lock_irqsave(&acm->read_lock, flags); tty_insert_flip_string(&acm->port, urb->transfer_buffer, urb->actual_length); + spin_unlock_irqrestore(&acm->read_lock, flags); + tty_flip_buffer_push(&acm->port); }