From: Wen Yang <[email protected]>

[ Upstream commit 68aab823c223646fab311f8a6581994facee66a0 ]

The variables 'window_interval' is u64 and do_div()
truncates it to 32 bits, which means it can test
non-zero and be truncated to zero for division.
The unit of window_interval is nanoseconds,
so its lower 32-bit is relatively easy to exceed.
Fix this issue by using div64_u64() instead.

Fixes: 7298de9cd725 ("sch_cake: Add ingress mode")
Signed-off-by: Wen Yang <[email protected]>
Cc: Kevin Darbyshire-Bryant <[email protected]>
Cc: Toke Høiland-Jørgensen <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Cong Wang <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Acked-by: Toke Høiland-Jørgensen <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 net/sched/sch_cake.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_cake.c
+++ b/net/sched/sch_cake.c
@@ -1769,7 +1769,7 @@ static s32 cake_enqueue(struct sk_buff *
                                                      q->avg_window_begin));
                        u64 b = q->avg_window_bytes * (u64)NSEC_PER_SEC;
 
-                       do_div(b, window_interval);
+                       b = div64_u64(b, window_interval);
                        q->avg_peak_bandwidth =
                                cake_ewma(q->avg_peak_bandwidth, b,
                                          b > q->avg_peak_bandwidth ? 2 : 8);


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