netdev - Re: [PATCH 1/1] netfilter: nft_fib: Fix for rpath check with VRF devices

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Message-ID: <20220930141048.GA10057@localhost.localdomain>
Date:   Fri, 30 Sep 2022 16:10:48 +0200
From:   Guillaume Nault <gnault@...hat.com>
To:     Florian Westphal <fw@...len.de>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        netfilter-devel@...r.kernel.org, Phil Sutter <phil@....cc>
Subject: Re: [PATCH 1/1] netfilter: nft_fib: Fix for rpath check with VRF
 devices

On Wed, Sep 28, 2022 at 01:39:08PM +0200, Florian Westphal wrote:
> diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c
> index 8970d0b4faeb..1d7e520d9966 100644
> --- a/net/ipv6/netfilter/nft_fib_ipv6.c
> +++ b/net/ipv6/netfilter/nft_fib_ipv6.c
> @@ -41,6 +41,9 @@ static int nft_fib6_flowi_init(struct flowi6 *fl6, const struct nft_fib *priv,
>  	if (ipv6_addr_type(&fl6->daddr) & IPV6_ADDR_LINKLOCAL) {
>  		lookup_flags |= RT6_LOOKUP_F_IFACE;
>  		fl6->flowi6_oif = get_ifindex(dev ? dev : pkt->skb->dev);
> +	} else if ((priv->flags & NFTA_FIB_F_IIF) &&
> +		   (netif_is_l3_master(dev) || netif_is_l3_slave(dev))) {
> +		fl6->flowi6_oif = dev->ifindex;
>  	}

I'm not very familiar with nft code, but it seems dev can be NULL here,
so netif_is_l3_master() can dereference a NULL pointer.

Shouldn't we test dev in the 'else if' condition?