[PATCH 4.19 37/77] net-sysfs: take the rtnl lock when accessing xps_rxqs_map and num_tc

[Greg Kroah-Hartman]

From: Antoine Tenart <aten...@kernel.org>

[ Upstream commit 4ae2bb81649dc03dfc95875f02126b14b773f7ab ]

Accesses to dev->xps_rxqs_map (when using dev->num_tc) should be
protected by the rtnl lock, like we do for netif_set_xps_queue. I didn't
see an actual bug being triggered, but let's be safe here and take the
rtnl lock while accessing the map in sysfs.

Fixes: 8af2c06ff4b1 ("net-sysfs: Add interface for Rx queue(s) map per Tx 
queue")
Signed-off-by: Antoine Tenart <aten...@kernel.org>
Reviewed-by: Alexander Duyck <alexanderdu...@fb.com>
Signed-off-by: Jakub Kicinski <k...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/core/net-sysfs.c |   23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1356,23 +1356,30 @@ static struct netdev_queue_attribute xps
 
 static ssize_t xps_rxqs_show(struct netdev_queue *queue, char *buf)
 {
+       int j, len, ret, num_tc = 1, tc = 0;
        struct net_device *dev = queue->dev;
        struct xps_dev_maps *dev_maps;
        unsigned long *mask, index;
-       int j, len, num_tc = 1, tc = 0;
 
        index = get_netdev_queue_index(queue);
 
+       if (!rtnl_trylock())
+               return restart_syscall();
+
        if (dev->num_tc) {
                num_tc = dev->num_tc;
                tc = netdev_txq_to_tc(dev, index);
-               if (tc < 0)
-                       return -EINVAL;
+               if (tc < 0) {
+                       ret = -EINVAL;
+                       goto err_rtnl_unlock;
+               }
        }
        mask = kcalloc(BITS_TO_LONGS(dev->num_rx_queues), sizeof(long),
                       GFP_KERNEL);
-       if (!mask)
-               return -ENOMEM;
+       if (!mask) {
+               ret = -ENOMEM;
+               goto err_rtnl_unlock;
+       }
 
        rcu_read_lock();
        dev_maps = rcu_dereference(dev->xps_rxqs_map);
@@ -1398,10 +1405,16 @@ static ssize_t xps_rxqs_show(struct netd
 out_no_maps:
        rcu_read_unlock();
 
+       rtnl_unlock();
+
        len = bitmap_print_to_pagebuf(false, buf, mask, dev->num_rx_queues);
        kfree(mask);
 
        return len < PAGE_SIZE ? len : -EINVAL;
+
+err_rtnl_unlock:
+       rtnl_unlock();
+       return ret;
 }
 
 static ssize_t xps_rxqs_store(struct netdev_queue *queue, const char *buf,