[PATCH] cdc-acm: fix consecutive writes while device is suspended

[Oliver Neukum]

CDC-ACM needs to handle one attempt to write to a suspended
device because we told the tty layer that there is room.
A second attempt may and must fail or we drop data.

Signed-off-by: Oliver Neukum <oneukum@xxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
---
 drivers/usb/class/cdc-acm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 900f7ff..7ad3105 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -646,10 +646,12 @@ static int acm_tty_write(struct tty_struct *tty,
 
 	usb_autopm_get_interface_async(acm->control);
 	if (acm->susp_count) {
-		if (!acm->delayed_wb)
+		if (!acm->delayed_wb) {
 			acm->delayed_wb = wb;
-		else
+		} else {
 			usb_autopm_put_interface_async(acm->control);
+			count = 0;
+		}
 		spin_unlock_irqrestore(&acm->write_lock, flags);
 		return count;	/* A white lie */
 	}
-- 
1.8.4.5



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