linux-hardening - Re: [PATCH][next] iavf: Replace one-element array with flexible-array member

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Date:   Tue, 23 May 2023 11:19:00 -0700
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        "Eric Dumazet" <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, <keescook@...omium.org>
CC:     <intel-wired-lan@...ts.osuosl.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-hardening@...r.kernel.org>,
        "Keller, Jacob E" <jacob.e.keller@...el.com>
Subject: Re: [PATCH][next] iavf: Replace one-element array with flexible-array
 member

On 5/15/2023 5:44 PM, Gustavo A. R. Silva wrote:
> One-element arrays are deprecated, and we are replacing them with flexible
> array members instead. So, replace one-element array with flexible-array
> member in struct iavf_qvlist_info, and refactor the rest of the code,
> accordingly.
> 
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -fstrict-flex-arrays=3 [1].
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/289
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>   drivers/net/ethernet/intel/iavf/iavf_client.c | 2 +-
>   drivers/net/ethernet/intel/iavf/iavf_client.h | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_client.c b/drivers/net/ethernet/intel/iavf/iavf_client.c
> index 93c903c02c64..782384b3aa38 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_client.c
> +++ b/drivers/net/ethernet/intel/iavf/iavf_client.c
> @@ -470,7 +470,7 @@ static int iavf_client_setup_qvlist(struct iavf_info *ldev,
>   
>   	v_qvlist_info = (struct virtchnl_rdma_qvlist_info *)qvlist_info;
>   	msg_size = struct_size(v_qvlist_info, qv_info,
> -			       v_qvlist_info->num_vectors - 1);
> +			       v_qvlist_info->num_vectors);

The problem is this mirrors the virtchnl struct 
(virtchnl_rdma_qvlist_info) so that structure needs to change as well... 
However, this goes back to the interface that virtchnl provides between 
PF and VF [1].

I think removing the iavf structure and directly using the virtchnl one 
would make sense. We'd need to adjust virtchnl and follow Kees' 
suggestion [2].

>   	adapter->client_pending |= BIT(VIRTCHNL_OP_CONFIG_RDMA_IRQ_MAP);
>   	err = iavf_aq_send_msg_to_pf(&adapter->hw,
> diff --git a/drivers/net/ethernet/intel/iavf/iavf_client.h b/drivers/net/ethernet/intel/iavf/iavf_client.h
> index c5d51d7dc7cc..500269bc0f5b 100644
> --- a/drivers/net/ethernet/intel/iavf/iavf_client.h
> +++ b/drivers/net/ethernet/intel/iavf/iavf_client.h
> @@ -53,7 +53,7 @@ struct iavf_qv_info {
>   
>   struct iavf_qvlist_info {
>   	u32 num_vectors;
> -	struct iavf_qv_info qv_info[1];
> +	struct iavf_qv_info qv_info[];
>   };
>   
>   #define IAVF_CLIENT_MSIX_ALL 0xFFFFFFFF

[1] 
https://lore.kernel.org/intel-wired-lan/f3674339c0390ced22b365101f2d3e3a2bf26845.camel@intel.com/
[2] https://lore.kernel.org/intel-wired-lan/202106091424.37E833794@keescook/