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Subject: Re: [PATCH v2] RDMA/core: Fix race when resolving IP address
To:     Parav Pandit <pandit.parav@gmail.com>
Cc:     Doug Ledford <dledford@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>,
        Leon Romanovsky <leon@kernel.org>,
        Parav Pandit <parav@mellanox.com>,
        linux-rdma <linux-rdma@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <1561711763-24705-1-git-send-email-dag.moxnes@oracle.com>
 <CAG53R5VQqqr0S6OU+13tcuxcvz922iuqoP-mWbaQERPc48964A@mail.gmail.com>
From:   Dag Moxnes <dag.moxnes@oracle.com>
Message-ID: <4e46889a-0b13-fa9b-fe8e-d9f6a44d714a@oracle.com>
Date:   Fri, 5 Jul 2019 11:03:08 +0200
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Den 05.07.2019 04:19, skrev Parav Pandit:
> On Fri, Jun 28, 2019 at 2:20 PM Dag Moxnes <dag.moxnes@oracle.com> 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.
>>
>> Signed-off-by: Dag Moxnes <dag.moxnes@oracle.com>
>> Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
>>
>> ---
>> v1 -> v2:
>>     * Modified implementation to improve readability
>> ---
>>   drivers/infiniband/core/addr.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/infiniband/core/addr.c b/drivers/infiniband/core/addr.c
>> index 2f7d141598..51323ffbc5 100644
>> --- a/drivers/infiniband/core/addr.c
>> +++ b/drivers/infiniband/core/addr.c
>> @@ -333,11 +333,14 @@ static int dst_fetch_ha(const struct dst_entry *dst,
>>          if (!n)
>>                  return -ENODATA;
>>
>> -       if (!(n->nud_state & NUD_VALID)) {
>> +       read_lock_bh(&n->lock);
>> +       if (n->nud_state & NUD_VALID) {
>> +               memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
>> +               read_unlock_bh(&n->lock);
>> +       } else {
>> +               read_unlock_bh(&n->lock);
>>                  neigh_event_send(n, NULL);
>>                  ret = -ENODATA;
>> -       } else {
>> -               memcpy(dev_addr->dst_dev_addr, n->ha, MAX_ADDR_LEN);
>>          }
>>
>>          neigh_release(n);
>> --
>> 2.20.1
>>
> Reviewed-by: Parav Pandit <parav@mellanox.com>
>
> A sample trace such as below in commit message would be good to have.
> Or the similar one that you noticed with ARP delete sequence.
>
> neigh_changeaddr()
>    neigh_flush_dev()
>     n->nud_state = NUD_NOARP;
>
> Having some issues with office outlook, so replying via gmail.

Hi Parav,

Thanks for your review. I'll add a sample trace to the commit message as

you suggest.


Regards,

-Dag