Messages in this thread | | | Date | Fri, 3 Mar 2023 15:18:21 +0300 | Subject | Re: [EXT] Re: [PATCH v0] qed/qed_dev: guard against a possible division by zero | From | Daniil Tatianin <> |
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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
>>>> * 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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