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xpp_usb: Fix potential corruption on clock rewind

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The xpp modules use time differences for various statistics. In one case
xpp_usb creates a histogram of the time it took the system to send USB
packets (URBs). The time difference is used (after adjustments) as an
index to that array.

However if the clock happens to go back at that exact point in time, we
get to write to an arbitrary negative index in this array.

Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
This commit is contained in:
Tzafrir Cohen 2016-01-13 12:19:04 +02:00
parent 4b242c3f84
commit ffdfdfb66b
1 changed files with 2 additions and 0 deletions
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2
drivers/dahdi/xpp/xpp_usb.c
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@ -890,6 +890,8 @@ static void xpp_send_callback(USB_PASS_CB(urb))
do_gettimeofday(&now);
xusb->last_tx = xframe->tv_submitted;
usec = usec_diff(&now, &xframe->tv_submitted);
if (usec < 0)
usec = 0; /* System clock jumped */
if (usec > xusb->max_tx_delay)
xusb->max_tx_delay = usec;
i = usec / USEC_BUCKET;