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

Greg Kroah-Hartman
2021-01-11T13:09:09Z

From: Antoine Tenart <atenart@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 <atenart@kernel.org>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@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,