Messages in this thread | | | Date | Tue, 14 Feb 2023 10:23:11 +0300 | Subject | Re: [PATCH v0] qed/qed_dev: guard against a possible division by zero | From | Daniil Tatianin <> |
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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. > * 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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