[PATCH 3.10 160/250] USB: serial: digi_acceleport: fix OOB-event processing

[Willy Tarreau]

From: Johan Hovold <johan@xxxxxxxxxx>

commit 2e46565cf622dd0534a9d8bffe152a577b48d7aa upstream.

A recent change claimed to fix an off-by-one error in the OOB-port
completion handler, but instead introduced such an error. This could
specifically led to modem-status changes going unnoticed, effectively
breaking TIOCMGET.

Note that the offending commit fixes a loop-condition underflow and is
marked for stable, but should not be backported without this fix.

Reported-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Fixes: 2d380889215f ("USB: serial: digi_acceleport: fix OOB data sanity
check")
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 drivers/usb/serial/digi_acceleport.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index 15b9cb3..e8d7c1b 100644
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -1498,7 +1498,7 @@ static int digi_read_oob_callback(struct urb *urb)
 		return -1;
 
 	/* handle each oob command */
-	for (i = 0; i < urb->actual_length - 4; i += 4) {
+	for (i = 0; i < urb->actual_length - 3; i += 4) {
 		opcode = buf[i];
 		line = buf[i + 1];
 		status = buf[i + 2];
-- 
2.8.0.rc2.1.gbe9624a