Re: ipv6: release dst in ping_v6_sendmsg

[Martin KaFai Lau <kafai@fb.com>]

On Fri, Sep 02, 2016 at 02:39:50PM -0400, Dave Jones wrote:
> Neither the failure or success paths of ping_v6_sendmsg release
> the dst it acquires.  This leads to a flood of warnings from
> "net/core/dst.c:288 dst_release" on older kernels that
> don't have 8bf4ada2e21378816b28205427ee6b0e1ca4c5f1 backported.
>
> That patch optimistically hoped this had been fixed post 3.10, but
> it seems at least one case wasn't, where I've seen this triggered
> a lot from machines doing unprivileged icmp sockets.
>
> Cc: Martin Lau <kafai@fb.com>
> Signed-off-by: Dave Jones <davej@codemonkey.org.uk>
>
> diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
> index 0900352c924c..0e983b694ee8 100644
> --- a/net/ipv6/ping.c
> +++ b/net/ipv6/ping.c
> @@ -126,8 +126,10 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>  	rt = (struct rt6_info *) dst;
>
>  	np = inet6_sk(sk);
> -	if (!np)
> -		return -EBADF;
> +	if (!np) {
> +		err = -EBADF;
> +		goto dst_err_out;
> +	}
>
>  	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
>  		fl6.flowi6_oif = np->mcast_oif;
> @@ -163,6 +165,9 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
>  	}
>  	release_sock(sk);
>
> +dst_err_out:
> +	dst_release(dst);
> +
>  	if (err)
>  		return err;
>

Acked-by: Martin KaFai Lau <kafai@fb.com>