netdev - Re: [PATCH net] net: ping6: Fix ping -6 with interface name

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Date:   Tue, 10 May 2022 14:27:18 -0600
From:   David Ahern <dsahern@...nel.org>
To:     Tariq Toukan <tariqt@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, Aya Levin <ayal@...dia.com>,
        Gal Pressman <gal@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>
Subject: Re: [PATCH net] net: ping6: Fix ping -6 with interface name

On 5/10/22 11:27 AM, Tariq Toukan wrote:
> From: Aya Levin <ayal@...dia.com>
> 
> When passing interface parameter to ping -6:
> $ ping -6 ::11:141:84:9 -I eth2
> Results in:
> PING ::11:141:84:10(::11:141:84:10) from ::11:141:84:9 eth2: 56 data bytes
> ping: sendmsg: Invalid argument
> ping: sendmsg: Invalid argument
> 
> Initialize the fl6's outgoing interface (OIF) before triggering
> ip6_datagram_send_ctl.
> 
> Fixes: 13651224c00b ("net: ping6: support setting basic SOL_IPV6 options via cmsg")
> Signed-off-by: Aya Levin <ayal@...dia.com>
> Reviewed-by: Gal Pressman <gal@...dia.com>
> Reviewed-by: Saeed Mahameed <saeedm@...dia.com>
> Signed-off-by: Tariq Toukan <tariqt@...dia.com>
> ---
>  net/ipv6/ping.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
> index ff033d16549e..83f014559c0d 100644
> --- a/net/ipv6/ping.c
> +++ b/net/ipv6/ping.c
> @@ -106,6 +106,8 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>  
>  		opt.tot_len = sizeof(opt);
>  		ipc6.opt = &opt;
> +		memset(&fl6, 0, sizeof(fl6));
> +		fl6.flowi6_oif = oif;
>  
>  		err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, &fl6, &ipc6);
>  		if (err < 0)

I agree that fl6 is used unitialized here, but right after this is:

        memset(&fl6, 0, sizeof(fl6));

        fl6.flowi6_proto = IPPROTO_ICMPV6;
        fl6.saddr = np->saddr;
        fl6.daddr = *daddr;
        fl6.flowi6_oif = oif;

so adding a memset before the call to ip6_datagram_send_ctl duplicates
the existing one. Best to move the memset before the 'if
(msg->msg_controllen) {'