Messages in this thread | | | From | Manish Chopra <> | Subject | RE: [EXT] Re: [PATCH v0] qed/qed_dev: guard against a possible division by zero | Date | Tue, 7 Mar 2023 17:50:49 +0000 |
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> -----Original Message----- > From: Daniil Tatianin <d-tatianin@yandex-team.ru> > Sent: Friday, March 3, 2023 5:48 PM > To: Manish Chopra <manishc@marvell.com>; Simon Horman > <simon.horman@corigine.com> > Cc: Ariel Elior <aelior@marvell.com>; David S. Miller > <davem@davemloft.net>; Eric Dumazet <edumazet@google.com>; Jakub > Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; Yuval Mintz > <Yuval.Mintz@qlogic.com>; netdev@vger.kernel.org; linux- > kernel@vger.kernel.org > Subject: Re: [EXT] Re: [PATCH v0] qed/qed_dev: guard against a possible > division by zero > > On 2/16/23 9:42 AM, Daniil Tatianin wrote: > > On 2/16/23 12:20 AM, Manish Chopra wrote: > >>> -----Original Message----- > >>> From: Daniil Tatianin <d-tatianin@yandex-team.ru> > >>> Sent: Tuesday, February 14, 2023 12:53 PM > >>> To: Simon Horman <simon.horman@corigine.com> > >>> Cc: Ariel Elior <aelior@marvell.com>; Manish Chopra > >>> <manishc@marvell.com>; David S. Miller <davem@davemloft.net>; Eric > >>> Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; > >>> Paolo Abeni <pabeni@redhat.com>; Yuval Mintz > >>> <Yuval.Mintz@qlogic.com>; netdev@vger.kernel.org; > >>> linux-kernel@vger.kernel.org > >>> Subject: [EXT] Re: [PATCH v0] qed/qed_dev: guard against a possible > >>> division by zero > >>> > >>> External Email > >>> > >>> -------------------------------------------------------------------- > >>> -- > >>> > >>> > >>> On 2/9/23 2:13 PM, Simon Horman wrote: > >>>> On Thu, Feb 09, 2023 at 01:38:13PM +0300, Daniil Tatianin wrote: > >>>>> Previously we would divide total_left_rate by zero if num_vports > >>>>> happened to be 1 because non_requested_count is calculated as > >>>>> num_vports - req_count. Guard against this by explicitly checking > >>>>> for zero when doing the division. > >>>>> > >>>>> Found by Linux Verification Center (linuxtesting.org) with the > >>>>> SVACE static analysis tool. > >>>>> > >>>>> Fixes: bcd197c81f63 ("qed: Add vport WFQ configuration APIs") > >>>>> Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru> > >>>>> --- > >>>>> drivers/net/ethernet/qlogic/qed/qed_dev.c | 2 +- > >>>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>>> > >>>>> diff --git a/drivers/net/ethernet/qlogic/qed/qed_dev.c > >>>>> b/drivers/net/ethernet/qlogic/qed/qed_dev.c > >>>>> index d61cd32ec3b6..90927f68c459 100644 > >>>>> --- a/drivers/net/ethernet/qlogic/qed/qed_dev.c > >>>>> +++ b/drivers/net/ethernet/qlogic/qed/qed_dev.c > >>>>> @@ -5123,7 +5123,7 @@ static int qed_init_wfq_param(struct > >>>>> qed_hwfn *p_hwfn, > >>>>> > >>>>> total_left_rate = min_pf_rate - total_req_min_rate; > >>>>> > >>>>> - left_rate_per_vp = total_left_rate / non_requested_count; > >>>>> + left_rate_per_vp = total_left_rate / (non_requested_count ?: > >>>>> +1); > >>>> > >>>> I don't know if num_vports can be 1. > >>>> But if it is then I agree that the above will be a divide by zero. > >>>> > >>>> I do, however, wonder if it would be better to either: > >>>> > >>>> * Treat this case as invalid and return with -EINVAL if num_vports > >>>> is 1; or > >>> I think that's a good idea considering num_vports == 1 is indeed an > >>> invalid value. > >>> I'd like to hear a maintainer's opinion on this. > >> Practically, this flow will only hit with presence of SR-IOV VFs. In > >> that case it's always expected to have num_vports > 1. > > > > In that case, should we add a check and return with -EINVAL otherwise? > > Thank you! > > > > Ping > It should be fine, please add some log indicating "Unexpected num_vports" before returning error.
Thanks, Manish
> >>>> * Skip both the calculation immediately above and the code > >>>> in the if condition below, which is the only place where > >>>> the calculated value is used, if num_vports is 1. > >>>> I don't think the if clause makes much sense if num_vports is > >>>> one.left_rate_per_vp is also used below the if clause, it is > >>>> assigned to > >>> .min_speed in a for loop. Looking at that code division by 1 seems > >>> to make sense to me in this case. > >>>> > >>>>> if (left_rate_per_vp < min_pf_rate / QED_WFQ_UNIT) { > >>>>> DP_VERBOSE(p_hwfn, NETIF_MSG_LINK, > >>>>> "Non WFQ configured vports rate [%d Mbps] is > >>>>> less > >>> than one > >>>>> percent of configured PF min rate[%d Mbps]\n", > >>>>> -- > >>>>> 2.25.1 > >>>>>
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