USB: serial: digi_acceleport: fix OOB-event processing

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@decadent.org.uk>
Fixes: 2d380889215f ("USB: serial: digi_acceleport: fix OOB data sanity
check")
Cc: stable <stable@vger.kernel.org>	# v2.6.30: 2d380889215f
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/digi_acceleport.c b/drivers/usb/serial/digi_acceleport.c
index ab78111e09680f47267cbe5fc7fe9a25ca5eea21..6537d3ca2797d8573236578e3088f6dbce1ce1b5 100644 (file)
--- a/drivers/usb/serial/digi_acceleport.c
+++ b/drivers/usb/serial/digi_acceleport.c
@@ -1500,7 +1500,7 @@ 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];