netdev - Re: [PATCH v1] qed/qed_dev: guard against a possible division by zero

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Date:   Thu, 9 Mar 2023 17:01:17 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Daniil Tatianin <d-tatianin@...dex-team.ru>
Cc:     Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Yuval Mintz <Yuval.Mintz@...gic.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] qed/qed_dev: guard against a possible division by zero

On Thu, Mar 09, 2023 at 03:56:36PM +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 validating num_vports at
> the beginning and returning an error otherwise.

Thanks,

I like this approach.

Reviewed-by: Simon Horman <simon.horman@...igine.com>

> 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@...dex-team.ru>
> ---
>  drivers/net/ethernet/qlogic/qed/qed_dev.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/ethernet/qlogic/qed/qed_dev.c b/drivers/net/ethernet/qlogic/qed/qed_dev.c
> index d61cd32ec3b6..9aaaf5ad3eb0 100644
> --- a/drivers/net/ethernet/qlogic/qed/qed_dev.c
> +++ b/drivers/net/ethernet/qlogic/qed/qed_dev.c
> @@ -5083,6 +5083,13 @@ static int qed_init_wfq_param(struct qed_hwfn *p_hwfn,
>  
>  	num_vports = p_hwfn->qm_info.num_vports;
>  
> +	if (num_vports < 2) {
> +		DP_NOTICE(p_hwfn,
> +			   "Unexpected num_vports: %d\n",
> +			   num_vports);

nit: the lines above are not indented correctly, however,
     I think that it's better yet if the DP_NOTICE is on a single line.

> +		return -EINVAL;
> +	}
> +
>  	/* Accounting for the vports which are configured for WFQ explicitly */
>  	for (i = 0; i < num_vports; i++) {
>  		u32 tmp_speed;
> -- 
> 2.25.1
>