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

[Chas Williams <3chas3@gmail.com>]

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;
> +	}
>   
>   	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;
> +	}
>   
>   	for (i = 0; i < slave_count && nb_pkts; i++) {
>   		uint16_t num_rx_slave;
>