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Date:   Thu, 5 Apr 2018 08:00:09 -0700
From:   Vadim Lomovtsev <Vadim.Lomovtsev@caviumnetworks.com>
To:     sgoutham@cavium.com, sunil.kovvuri@gmail.com, rric@kernel.org,
        linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, davem@davemloft.net
Cc:     dnelson@redhat.com, gustavo@embeddedor.com,
        Vadim Lomovtsev <Vadim.Lomovtsev@cavium.com>
Subject: Re: [PATCH] net: thunderx: rework mac addresses list to u64 array
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[correct Roberts' address]

On Thu, Apr 05, 2018 at 07:57:56AM -0700, Vadim Lomovtsev wrote:
> From: Vadim Lomovtsev <Vadim.Lomovtsev@cavium.com>
> 
> It is too expensive to pass u64 values via linked list, instead
> allocate array for them by overall number of mac addresses from netdev.
> 
> This eventually removes multiple kmalloc() calls, aviod memory
> fragmentation and allow to put single null check on kmalloc
> return value in order to prevent a potential null pointer dereference.
> 
> Addresses-Coverity-ID: 1467429 ("Dereference null return value")
> Fixes: 37c3347eb247 ("net: thunderx: add ndo_set_rx_mode callback implementation for VF")
> Signed-off-by: Vadim Lomovtsev <Vadim.Lomovtsev@cavium.com>
> ---
>  drivers/net/ethernet/cavium/thunder/nic.h        |  7 +-----
>  drivers/net/ethernet/cavium/thunder/nicvf_main.c | 28 +++++++++---------------
>  2 files changed, 11 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cavium/thunder/nic.h b/drivers/net/ethernet/cavium/thunder/nic.h
> index 5fc46c5a4f36..da052159f014 100644
> --- a/drivers/net/ethernet/cavium/thunder/nic.h
> +++ b/drivers/net/ethernet/cavium/thunder/nic.h
> @@ -265,14 +265,9 @@ struct nicvf_drv_stats {
>  
>  struct cavium_ptp;
>  
> -struct xcast_addr {
> -	struct list_head list;
> -	u64              addr;
> -};
> -
>  struct xcast_addr_list {
> -	struct list_head list;
>  	int              count;
> +	u64              mc[0];
>  };
>  
>  struct nicvf_work {
> diff --git a/drivers/net/ethernet/cavium/thunder/nicvf_main.c b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> index 1e9a31fef729..a26d8bc92e01 100644
> --- a/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> +++ b/drivers/net/ethernet/cavium/thunder/nicvf_main.c
> @@ -1929,7 +1929,7 @@ static void nicvf_set_rx_mode_task(struct work_struct *work_arg)
>  						  work.work);
>  	struct nicvf *nic = container_of(vf_work, struct nicvf, rx_mode_work);
>  	union nic_mbx mbx = {};
> -	struct xcast_addr *xaddr, *next;
> +	u8 idx = 0;
>  
>  	if (!vf_work)
>  		return;
> @@ -1956,16 +1956,10 @@ static void nicvf_set_rx_mode_task(struct work_struct *work_arg)
>  	/* check if we have any specific MACs to be added to PF DMAC filter */
>  	if (vf_work->mc) {
>  		/* now go through kernel list of MACs and add them one by one */
> -		list_for_each_entry_safe(xaddr, next,
> -					 &vf_work->mc->list, list) {
> +		for (idx = 0; idx < vf_work->mc->count; idx++) {
>  			mbx.xcast.msg = NIC_MBOX_MSG_ADD_MCAST;
> -			mbx.xcast.data.mac = xaddr->addr;
> +			mbx.xcast.data.mac = vf_work->mc->mc[idx];
>  			nicvf_send_msg_to_pf(nic, &mbx);
> -
> -			/* after receiving ACK from PF release memory */
> -			list_del(&xaddr->list);
> -			kfree(xaddr);
> -			vf_work->mc->count--;
>  		}
>  		kfree(vf_work->mc);
>  	}
> @@ -1996,17 +1990,15 @@ static void nicvf_set_rx_mode(struct net_device *netdev)
>  			mode |= BGX_XCAST_MCAST_FILTER;
>  			/* here we need to copy mc addrs */
>  			if (netdev_mc_count(netdev)) {
> -				struct xcast_addr *xaddr;
> -
> -				mc_list = kmalloc(sizeof(*mc_list), GFP_ATOMIC);
> -				INIT_LIST_HEAD(&mc_list->list);
> +				mc_list = kmalloc(sizeof(*mc_list) +
> +						  sizeof(u64) * netdev_mc_count(netdev),
> +						  GFP_ATOMIC);
> +				if (unlikely(!mc_list))
> +					return;
> +				mc_list->count = 0;
>  				netdev_hw_addr_list_for_each(ha, &netdev->mc) {
> -					xaddr = kmalloc(sizeof(*xaddr),
> -							GFP_ATOMIC);
> -					xaddr->addr =
> +					mc_list->mc[mc_list->count] =
>  						ether_addr_to_u64(ha->addr);
> -					list_add_tail(&xaddr->list,
> -						      &mc_list->list);
>  					mc_list->count++;
>  				}
>  			}
> -- 
> 2.14.3
>