netdev - Re: [PATCH net-next] net, bonding: Disallow vlan+srcmac with XDP

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Date:   Fri, 13 Aug 2021 15:40:13 -0400
From:   Jonathan Toppins <jtoppins@...hat.com>
To:     Jussi Maki <joamaki@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net, bonding: Disallow vlan+srcmac with XDP

On 8/12/21 10:52 AM, Jussi Maki wrote:
> The new vlan+srcmac xmit policy is not implementable with XDP since
> in many cases the 802.1Q payload is not present in the packet. This
> can be for example due to hardware offload or in the case of veth
> due to use of skbuffs internally.
> 
> This also fixes the NULL deref with the vlan+srcmac xmit policy
> reported by Jonathan Toppins by additionally checking the skb
> pointer.
> 
> Fixes: a815bde56b15 ("net, bonding: Refactor bond_xmit_hash for use with xdp_buff")
> Reported-by: Jonathan Toppins <jtoppins@...hat.com>
> Signed-off-by: Jussi Maki <joamaki@...il.com>

Looks good, thanks.

Reviewed-by: Jonathan Toppins <jtoppins@...hat.com>

> ---
>   drivers/net/bonding/bond_main.c | 18 +++++++++++-------
>   1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index c0db4e2b2462..04158a8368e4 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -322,9 +322,15 @@ static bool bond_xdp_check(struct bonding *bond)
>   	switch (BOND_MODE(bond)) {
>   	case BOND_MODE_ROUNDROBIN:
>   	case BOND_MODE_ACTIVEBACKUP:
> +		return true;
>   	case BOND_MODE_8023AD:
>   	case BOND_MODE_XOR:
> -		return true;
> +		/* vlan+srcmac is not supported with XDP as in most cases the 802.1q
> +		 * payload is not in the packet due to hardware offload.
> +		 */
> +		if (bond->params.xmit_policy != BOND_XMIT_POLICY_VLAN_SRCMAC)
> +			return true;
> +		fallthrough;
>   	default:
>   		return false;
>   	}
> @@ -3744,9 +3750,9 @@ static bool bond_flow_ip(struct sk_buff *skb, struct flow_keys *fk, const void *
>   
>   static u32 bond_vlan_srcmac_hash(struct sk_buff *skb, const void *data, int mhoff, int hlen)
>   {
> -	struct ethhdr *mac_hdr;
>   	u32 srcmac_vendor = 0, srcmac_dev = 0;
> -	u16 vlan;
> +	struct ethhdr *mac_hdr;
> +	u16 vlan = 0;
>   	int i;
>   
>   	data = bond_pull_data(skb, data, hlen, mhoff + sizeof(struct ethhdr));
> @@ -3760,10 +3766,8 @@ static u32 bond_vlan_srcmac_hash(struct sk_buff *skb, const void *data, int mhof
>   	for (i = 3; i < ETH_ALEN; i++)
>   		srcmac_dev = (srcmac_dev << 8) | mac_hdr->h_source[i];
>   
> -	if (!skb_vlan_tag_present(skb))
> -		return srcmac_vendor ^ srcmac_dev;
> -
> -	vlan = skb_vlan_tag_get(skb);
> +	if (skb && skb_vlan_tag_present(skb))
> +		vlan = skb_vlan_tag_get(skb);
>   
>   	return vlan ^ srcmac_vendor ^ srcmac_dev;
>   }
>