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

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Date:   Thu, 18 Jul 2019 12:03:01 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     dsahern@...il.com
Cc:     idosch@...sch.org, netdev@...r.kernel.org, alexpe@...lanox.com,
        mlxsw@...lanox.com, idosch@...lanox.com
Subject: Re: [PATCH net] ipv6: Unlink sibling route in case of failure

From: David Ahern <dsahern@...il.com>
Date: Thu, 18 Jul 2019 08:21:01 -0600

> 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>

Applied and queued up for -stable.

Since I've done a bunch of ipv6 routing fix backports through David's
refactoring and cleanups, I'll give this one a try too :-) If I run
into problems I'll ask for help.

Thanks.