cdc-acm: fix BREAK rx code path adding necessary calls

stable inclusion
from stable-5.10.28
commit e700e3aec303597851f3113b0837fde7af44223f
bugzilla: 51779

--------------------------------

commit 08dff274 upstream.

Counting break events is nice but we should actually report them to
the tty layer.

Fixes: 5a6a62bd ("cdc-acm: add TIOCMIWAIT")
Signed-off-by: NOliver Neukum <oneukum@suse.com>
Link: https://lore.kernel.org/r/20210311133714.31881-1-oneukum@suse.com
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: N  Weilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/usb/class/cdc-acm.c

@@ -313,8 +313,10 @@ static void acm_process_notification(struct acm *acm, unsigned char *buf)
 			acm->iocount.dsr++;
 		if (difference & ACM_CTRL_DCD)
 			acm->iocount.dcd++;
-		if (newctrl & ACM_CTRL_BRK)
+		if (newctrl & ACM_CTRL_BRK) {
 			acm->iocount.brk++;
+			tty_insert_flip_char(&acm->port, 0, TTY_BREAK);
+		}
 		if (newctrl & ACM_CTRL_RI)
 			acm->iocount.rng++;
 		if (newctrl & ACM_CTRL_FRAMING)