netdev - Re: [PATCH] ipv6: Fix nexthop refcnt leak when creating ipv6 route info

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Message-ID: <330e3acc-dff5-a59e-e138-97ffbb6e7892@gmail.com>
Date:   Sat, 25 Jul 2020 18:07:49 -0600
From:   David Ahern <dsahern@...il.com>
To:     Xiyu Yang <xiyuyang19@...an.edu.cn>,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Xin Tan <tanxin.ctf@...il.com>
Subject: Re: [PATCH] ipv6: Fix nexthop refcnt leak when creating ipv6 route
 info

On 7/25/20 2:02 AM, Xiyu Yang wrote:
> ip6_route_info_create() invokes nexthop_get(), which increases the
> refcount of the "nh".
> 
> When ip6_route_info_create() returns, local variable "nh" becomes
> invalid, so the refcount should be decreased to keep refcount balanced.

I forgot to write the test case for this very code path in
tools/testing/selftests/net/fib_nexthops.sh. If you have the time, it
goes in ipv6_fcnal_runtime() - see the last 'TO-DO' item.

> 
> The reference counting issue happens in one exception handling path of
> ip6_route_info_create(). When nexthops can not be used with source
> routing, the function forgets to decrease the refcnt increased by
> nexthop_get(), causing a refcnt leak.
> 
> Fix this issue by pulling up the error source routing handling when
> nexthops can not be used with source routing.
> 

Fixes: f88d8ea67fbd ("ipv6: Plumb support for nexthop object in a
fib6_info")

> Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
> Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
> ---
>  net/ipv6/route.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 


Reviewed-by: David Ahern <dsahern@...nel.org>