netdev - Re: [PATCH] iwlwifi: d3: use struct

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Message-ID: <CAGXu5jJxbFzKsV1=xHiKtcx+61QBsK0LYMrwo1vGNWgALzqakw@mail.gmail.com>
Date:   Thu, 23 Aug 2018 20:03:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Intel Linux Wireless <linuxwifi@...el.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iwlwifi: d3: use struct_size() in kzalloc()

On Thu, Aug 23, 2018 at 6:15 PM, Gustavo A. R. Silva
<gustavo@...eddedor.com> wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
>
> struct foo {
>         int stuff;
>         void *entry[];
> };
>
> instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);
>
> Instead of leaving these open-coded and prone to type mistakes, we can
> now use the new struct_size() helper:
>
> instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);
>
> This issue was detected with the help of Coccinelle.
>
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  drivers/net/wireless/intel/iwlwifi/mvm/d3.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/d3.c b/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
> index 79bdae9..6960318 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
> +++ b/drivers/net/wireless/intel/iwlwifi/mvm/d3.c
> @@ -1769,8 +1769,7 @@ static void iwl_mvm_query_netdetect_reasons(struct iwl_mvm *mvm,
>                 n_matches = 0;
>         }
>
> -       net_detect = kzalloc(sizeof(*net_detect) +
> -                            (n_matches * sizeof(net_detect->matches[0])),
> +       net_detect = kzalloc(struct_size(net_detect, matches, n_matches),
>                              GFP_KERNEL);
>         if (!net_detect || !n_matches)
>                 goto out_report_nd;
> @@ -1785,8 +1784,7 @@ static void iwl_mvm_query_netdetect_reasons(struct iwl_mvm *mvm,
>                 for (j = 0; j < SCAN_OFFLOAD_MATCHING_CHANNELS_LEN; j++)
>                         n_channels += hweight8(fw_match->matching_channels[j]);
>
> -               match = kzalloc(sizeof(*match) +
> -                               (n_channels * sizeof(*match->channels)),
> +               match = kzalloc(struct_size(match, channels, n_channels),
>                                 GFP_KERNEL);
>                 if (!match)
>                         goto out_report_nd;
> --
> 2.7.4
>



-- 
Kees Cook
Pixel Security