[PATCH 5.10 022/145] net-sysfs: take the rtnl lock when accessing xps_cpus_map and num_tc

Greg Kroah-Hartman
2021-01-11T13:35:38Z

From: Antoine Tenart <atenart@kernel.org>

[ Upstream commit fb25038586d0064123e393cadf1fadd70a9df97a ]

Accesses to dev->xps_cpus_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: 184c449f91fe ("net: Add support for XPS with QoS via traffic classes")
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 | 29 ++++++++++++++++++++++-------
1 file changed, 22 insertions(+), 7 deletions(-)

--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1317,8 +1317,8 @@ static const struct attribute_group dql_
static ssize_t xps_cpus_show(struct netdev_queue *queue,
char *buf)
{
+ int cpu, len, ret, num_tc = 1, tc = 0;
struct net_device *dev = queue->dev;
- int cpu, len, num_tc = 1, tc = 0;
struct xps_dev_maps *dev_maps;
cpumask_var_t mask;
unsigned long index;
@@ -1328,22 +1328,31 @@ static ssize_t xps_cpus_show(struct netd

index = get_netdev_queue_index(queue);

+ if (!rtnl_trylock())
+ return restart_syscall();
+
if (dev->num_tc) {
/* Do not allow XPS on subordinate device directly */
num_tc = dev->num_tc;
- if (num_tc < 0)
- return -EINVAL;
+ if (num_tc < 0) {
+ ret = -EINVAL;
+ goto err_rtnl_unlock;
+ }

/* If queue belongs to subordinate dev use its map */
dev = netdev_get_tx_queue(dev, index)->sb_dev ? : dev;

tc = netdev_txq_to_tc(dev, index);
- if (tc < 0)
- return -EINVAL;
+ if (tc < 0) {
+ ret = -EINVAL;
+ goto err_rtnl_unlock;
+ }
}

- if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
- return -ENOMEM;
+ if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) {
+ ret = -ENOMEM;
+ goto err_rtnl_unlock;
+ }

rcu_read_lock();
dev_maps = rcu_dereference(dev->xps_cpus_map);
@@ -1366,9 +1375,15 @@ static ssize_t xps_cpus_show(struct netd
}
rcu_read_unlock();

+ rtnl_unlock();
+
len = snprintf(buf, PAGE_SIZE, "%*pb\n", cpumask_pr_args(mask));
free_cpumask_var(mask);
return len < PAGE_SIZE ? len : -EINVAL;
+
+err_rtnl_unlock:
+ rtnl_unlock();
+ return ret;
}

static ssize_t xps_cpus_store(struct netdev_queue *queue,