net/mlx5: fix use after free when releasing Tx queues

In function mlx5_dev_configure, dev->data->tx_queues is assigned
to priv->txqs. When a member is removed from a bond, the function
eth_dev_tx_queue_config is called to release dev->data->tx_queues.
However, function mlx5_dev_close will access priv->txqs again and
cause the use after free problem.

In function mlx5_dev_close, before free priv->txqs, we add a check
that dev->data->tx_queues is not NULL.

build/app/dpdk-testpmd -c7 -a 0000:08:00.2 --  -i --nb-cores=2
--total-num-mbufs=2048

testpmd> port stop 0
testpmd> create bonding device 4 0
testpmd> add bonding member 0 1
testpmd> remove bonding member 0 1
testpmd> quit

ASan reports:
==2571911==ERROR: AddressSanitizer: heap-use-after-free on address
0x000174529880 at pc 0x0000113c8440 bp 0xffffefae0ea0 sp 0xffffefae0eb0
READ of size 8 at 0x000174529880 thread T0
    #0 0x113c843c in mlx5_txq_release ../drivers/net/mlx5/mlx5_txq.c:
1203
    #1 0xffdb53c in mlx5_dev_close ../drivers/net/mlx5/mlx5.c:2286
    #2 0xe12dc0 in rte_eth_dev_close ../lib/ethdev/rte_ethdev.c:1877
    #3 0x6bac1c in close_port ../app/test-pmd/testpmd.c:3540
    #4 0x6bc320 in pmd_test_exit ../app/test-pmd/testpmd.c:3808
    #5 0x6c1a94 in main ../app/test-pmd/testpmd.c:4759
    #6 0xffff9328f038  (/usr/lib64/libc.so.6+0x2b038)
    #7 0xffff9328f110 in __libc_start_main (/usr/lib64/libc.so.6+
0x2b110)

Fixes: 6e78005 ("net/mlx5: add reference counter on DPDK Tx queues")
Cc: stable@dpdk.org

Reported-by: Yunjian Wang <wangyunjian@huawei.com>
Signed-off-by: Pengfei Sun <sunpengfei16@huawei.com>
Acked-by: Dariusz Sosnowski <dsosnowski@nvidia.com>

drivers/net/mlx5/mlx5.c

@@ -2362,7 +2362,7 @@ mlx5_dev_close(struct rte_eth_dev *dev)
 		mlx5_free(priv->rxq_privs);
 		priv->rxq_privs = NULL;
 	}
-	if (priv->txqs != NULL) {
+	if (priv->txqs != NULL && dev->data->tx_queues != NULL) {
 		/* XXX race condition if mlx5_tx_burst() is still running. */
 		rte_delay_us_sleep(1000);
 		for (i = 0; (i != priv->txqs_n); ++i)