Re: [PATCH] net/sched: cbs: perform rate conversions in signed 64-bit arithmetic

[Vinicius Costa Gomes]

Jack Wang <163wangjack@xxxxxxxxx> writes:

> cbs_set_port_rate() and cbs_change() multiply link rates and slope values
> by BYTES_PER_KBIT, an unsigned long constant.  On 32-bit architectures,
> the multiplications therefore take place in 32-bit unsigned arithmetic
> before the results are assigned to s64 fields.
>
> For port rates above approximately 34.36 Gbit/s this wraps port_rate.
> The same conversion turns a negative sendslope into a large positive
> value, reversing the CBS credit adjustment.  This affects software CBS;
> port_rate is also refreshed on NETDEV_UP and NETDEV_CHANGE notifications.
>
> Cast the first operand of each multiplication to s64 so all intermediate
> operations use signed 64-bit arithmetic and preserve the value's sign on
> every architecture.
>
> Fixes: 585d763af09c ("net/sched: Introduce Credit Based Shaper (CBS) qdisc")
> Fixes: 397006ba5d918 ("net/sched: cbs: Fix integer overflow in cbs_set_port_rate()")
>
> Signed-off-by: Jack Wang <163wangjack@xxxxxxxxx>
> ---

Acked-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>


Cheers,
-- 
Vinicius