netdev - Re: [PATCH net-next 1/6] nexthop: dereference nh only once in nexthop_select

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Message-ID: <ecd765d8-4e83-dd20-5d71-8c4bb7b30639@gmail.com>
Date:   Mon, 18 May 2020 21:25:49 -0600
From:   David Ahern <dsahern@...il.com>
To:     Roopa Prabhu <roopa@...ulusnetworks.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, nikolay@...ulusnetworks.com,
        jiri@...lanox.com, idosch@...lanox.com, petrm@...lanox.com
Subject: Re: [PATCH net-next 1/6] nexthop: dereference nh only once in
 nexthop_select_path

On 5/18/20 8:14 PM, Roopa Prabhu wrote:
> From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> 
> the ->nh pointer might become suddenly null while we're selecting the
> path and we may dereference it. Dereference it only once in the
> beginning and use that if it's not null, we rely on the refcounting and
> rcu to protect against use-after-free. (This is needed for later
> vxlan patches that exposes the problem)
> 
> Signed-off-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
> ---
>  net/ipv4/nexthop.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 

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

Should this be a bug fix? Any chance the route path can hit it?