netdev - Re: [PATCH net] ipv6: Unlink sibling route in case of failure

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Date:   Thu, 18 Jul 2019 08:21:01 -0600
From:   David Ahern <dsahern@...il.com>
To:     Ido Schimmel <idosch@...sch.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, alexpe@...lanox.com, mlxsw@...lanox.com,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net] ipv6: Unlink sibling route in case of failure

On 7/17/19 2:39 PM, Ido Schimmel wrote:
> From: Ido Schimmel <idosch@...lanox.com>
> 
> When a route needs to be appended to an existing multipath route,
> fib6_add_rt2node() first appends it to the siblings list and increments
> the number of sibling routes on each sibling.
> 
> Later, the function notifies the route via call_fib6_entry_notifiers().
> In case the notification is vetoed, the route is not unlinked from the
> siblings list, which can result in a use-after-free.
> 
> Fix this by unlinking the route from the siblings list before returning
> an error.
> 
> Audited the rest of the call sites from which the FIB notification chain
> is called and could not find more problems.
> 
> Fixes: 2233000cba40 ("net/ipv6: Move call_fib6_entry_notifiers up for route adds")
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Reported-by: Alexander Petrovskiy <alexpe@...lanox.com>
> ---
> Dave, this will not apply cleanly to stable trees due to recent changes
> in net-next. I can prepare another patch for stable if needed.
> ---
>  net/ipv6/ip6_fib.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 

Thanks for the fix, Ido. I can help with the ports as well.

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