Re: [dpdk-dev] [dpdk-stable] [PATCH 2/2] net/bonding: avoid the next active slave going out of bound

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 2/18/2019 3:25 PM, Ferruh Yigit wrote:
> On 2/11/2019 10:25 AM, Parthasarathy, JananeeX M wrote:
>> Hi
>>
>>> -----Original Message-----
>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Chas Williams
>>> Sent: Saturday, February 09, 2019 6:47 PM
>>> To: Hyong Youb Kim <hyonkim@cisco.com>; Yigit, Ferruh
>>> <ferruh.yigit@intel.com>; Doherty, Declan <declan.doherty@intel.com>; Chas
>>> Williams <chas3@att.com>
>>> Cc: dev@dpdk.org; stable@dpdk.org
>>> Subject: Re: [dpdk-dev] [PATCH 2/2] net/bonding: avoid the next active slave
>>> going out of bound
>>>
>>>
>>>
>>> On 1/10/19 5:22 AM, Hyong Youb Kim wrote:
>>>> For bonding modes like broadcast that use bond_ethdev_rx_burst(), it
>>>> is fairly easy to produce a crash simply by bringing a slave port's
>>>> link down. When slave links go down, the driver on one thread reduces
>>>> active_slave_count via the LSC callback and deactivate_slave(). At the
>>>> same time, bond_ethdev_rx_burst() running on a forwarding thread may
>>>> increment active_slave (next active slave) beyond active_slave_count.
>>>> Here is a typical sequence of events.
>>>>
>>>> At time 0:
>>>> active_slave_count = 3
>>>> active_slave = 2
>>>>
>>>> At time 1:
>>>> A slave link goes down.
>>>> Thread 0 (main) reduces active_slave_count to 2.
>>>>
>>>> At time 2:
>>>> Thread 1 (forwarding) executes bond_ethdev_rx_burst().
>>>> - Reads active_slave_count = 2.
>>>> - Increments active_slave at the end to 3.
>>>>
>>>>  From this point on, everytime bond_ethdev_rx_burst() runs,
>>>> active_slave increments by one, eventually going well out of bound of
>>>> the active_slaves array and causing a crash.
>>>>
>>>> Make the rx burst function to first check that active_slave is within
>>>> bound. If not, reset it to 0 to avoid out-of-range array access.
>>>>
>>>> Fixes: e1110e977648 ("net/bonding: fix Rx slave fairness")
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: Hyong Youb Kim <hyonkim@cisco.com>
>>>
>>> Acked-by: Chas Williams <chas3@att.com>
>>>
>>>> ---
>>>>   drivers/net/bonding/rte_eth_bond_pmd.c | 14 ++++++++++++++
>>>>   1 file changed, 14 insertions(+)
>>>>
>>>> diff --git a/drivers/net/bonding/rte_eth_bond_pmd.c
>>>> b/drivers/net/bonding/rte_eth_bond_pmd.c
>>>> index daf2440cd..bc2405e54 100644
>>>> --- a/drivers/net/bonding/rte_eth_bond_pmd.c
>>>> +++ b/drivers/net/bonding/rte_eth_bond_pmd.c
>>>> @@ -68,6 +68,15 @@ bond_ethdev_rx_burst(void *queue, struct rte_mbuf
>>> **bufs, uint16_t nb_pkts)
>>>>   	internals = bd_rx_q->dev_private;
>>>>   	slave_count = internals->active_slave_count;
>>>>   	active_slave = internals->active_slave;
>>>> +	/*
>>>> +	 * Reset the active slave index, in case active_slave goes out
>>>> +	 * of bound.  It can hapen when slave links go down, and
>>>> +	 * another thread (LSC callback) shrinks the slave count.
>>>> +	 */
>>>> +	if (active_slave >= slave_count) {
>>>> +		internals->active_slave = 0;
>>>> +		active_slave = 0;
>>>> +	}
>>
>> Instead of introducing new conditions again at the top of functions, it would be better to check greater than, equal to >= instead of the equal to  in below condition.
>> if (++internals->active_slave == slave_count)
>>                 internals->active_slave = 0;
>>
>> Thereby we can reduce the multiple if conditions and still ensure internals->active_slave points to correct index always.
>>
>>>>
>>>>   	for (i = 0; i < slave_count && nb_pkts; i++) {
>>>>   		uint16_t num_rx_slave;
>>>> @@ -273,6 +282,11 @@ bond_ethdev_rx_burst_8023ad_fast_queue(void
>>> *queue, struct rte_mbuf **bufs,
>>>>   	active_slave = internals->active_slave;
>>>>   	memcpy(slaves, internals->active_slaves,
>>>>   			sizeof(internals->active_slaves[0]) * slave_count);
>>>> +	/* active_slave may go out of bound. See bond_ethdev_rx_burst() */
>>>> +	if (active_slave >= slave_count) {
>>>> +		internals->active_slave = 0;
>>>> +		active_slave = 0;
>>>> +	}
>>
>> Same as above comment would be better.
>>>>
>>>>   	for (i = 0; i < slave_count && nb_pkts; i++) {
>>>>   		uint16_t num_rx_slave;
>>>>
>>
>> It would be better to check the internals->active_slave during deactivate_slave() as well in rte_eth_bond_api.c.
>> Since slave counts would be decremented during de-activation and resetting here appropriately would be better.
>>
>> Regards
>> M.P.Jananee
> 
> 
> I don't see this comment on the patchwork, can you double check if your comment
> hit the mailing list?

For record, this patch superseded by:
https://patches.dpdk.org/patch/50346/