netdev - Re: [PATCH net] ipv6: do not leave garbage in rt->fib6

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Message-ID: <5c82ffec-bb35-9bc9-38f4-95962691641a@gmail.com>
Date:   Fri, 5 Oct 2018 10:29:36 -0600
From:   David Ahern <dsahern@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net] ipv6: do not leave garbage in rt->fib6_metrics

On 10/5/18 10:17 AM, Eric Dumazet wrote:
> In case ip_fib_metrics_init() returns an error, we better
> rewrite rt->fib6_metrics with &dst_default_metrics so that
> we do not crash later in ip_fib_metrics_put()
> 
> Fixes: 767a2217533f ("net: common metrics init helper for FIB entries")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Where is syzbot sending the reports? I don't see it on netdev. I would
like to understand how it triggered the failure of a 68-byte malloc.


> ---
>  net/ipv6/route.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 6c1d817151cae45421dc976c5ea082b4115650be..74d97addf1af20dda0c2b6a2018e88696f9f7d5a 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2976,6 +2976,8 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
>  	rt->fib6_metrics = ip_fib_metrics_init(net, cfg->fc_mx, cfg->fc_mx_len);
>  	if (IS_ERR(rt->fib6_metrics)) {
>  		err = PTR_ERR(rt->fib6_metrics);
> +		/* Do not leave garbage there. */
> +		rt->fib6_metrics = (struct dst_metrics *)&dst_default_metrics;
>  		goto out;
>  	}
>  
> 

Reviewed-by: David Ahern <dsahern@...il.com>

Thanks, Eric.