linux-kernel - Re: [PATCH v3] RDMA/core: Fix race when resolving IP address

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Message-ID: <4b9ae7b8-310c-e0b6-7a8e-33e6d5bef83d@oracle.com>
Date:   Mon, 8 Jul 2019 20:47:38 +0200
From:   Dag Moxnes <dag.moxnes@...cle.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     dledford@...hat.com, leon@...nel.org, parav@...lanox.com,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] RDMA/core: Fix race when resolving IP address

Thanks Jason,

Regards,
Dag

Den 08.07.2019 19:50, skrev Jason Gunthorpe:
> On Mon, Jul 08, 2019 at 01:16:24PM +0200, Dag Moxnes wrote:
>> Use neighbour lock when copying MAC address from neighbour data struct
>> in dst_fetch_ha.
>>
>> When not using the lock, it is possible for the function to race with
>> neigh_update, causing it to copy an invalid MAC address.
>>
>> It is possible to provoke this error by calling rdma_resolve_addr in a
>> tight loop, while deleting the corresponding ARP entry in another tight
>> loop.
>>
>> This will cause the race shown it the following sample trace:
>>
>> rdma_resolve_addr()
>>    rdma_resolve_ip()
>>      addr_resolve()
>>        addr_resolve_neigh()
>>          fetch_ha()
>>            dst_fetch_ha()
>>              n->nud_state == NUD_VALID
> It isn't nud_state that is the problem here, it is the parallel
> memcpy's onto ha. I fixed the commit message
>
> This could also have been solved by using the ha_lock, but I don't
> think we have a reason to particularly over-optimize this.
>
>>   drivers/infiniband/core/addr.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
> Applied to for-next, thanks
>
> Jason