From: Antoine Tenart atenart@kernel.org
[ Upstream commit 1ad58225dba3f2f598d2c6daed4323f24547168f ]
Two race conditions can be triggered when storing xps cpus, resulting in various oops and invalid memory accesses:
1. Calling netdev_set_num_tc while netif_set_xps_queue:
- netif_set_xps_queue uses dev->tc_num as one of the parameters to compute the size of new_dev_maps when allocating it. dev->tc_num is also used to access the map, and the compiler may generate code to retrieve this field multiple times in the function.
- netdev_set_num_tc sets dev->tc_num.
If new_dev_maps is allocated using dev->tc_num and then dev->tc_num is set to a higher value through netdev_set_num_tc, later accesses to new_dev_maps in netif_set_xps_queue could lead to accessing memory outside of new_dev_maps; triggering an oops.
2. Calling netif_set_xps_queue while netdev_set_num_tc is running:
2.1. netdev_set_num_tc starts by resetting the xps queues, dev->tc_num isn't updated yet.
2.2. netif_set_xps_queue is called, setting up the map with the *old* dev->num_tc.
2.3. netdev_set_num_tc updates dev->tc_num.
2.4. Later accesses to the map lead to out of bound accesses and oops.
A similar issue can be found with netdev_reset_tc.
One way of triggering this is to set an iface up (for which the driver uses netdev_set_num_tc in the open path, such as bnx2x) and writing to xps_cpus in a concurrent thread. With the right timing an oops is triggered.
Both issues have the same fix: netif_set_xps_queue, netdev_set_num_tc and netdev_reset_tc should be mutually exclusive. We do that by taking the rtnl lock in xps_cpus_store.
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 | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -1396,7 +1396,13 @@ static ssize_t xps_cpus_store(struct net return err; }
+ if (!rtnl_trylock()) { + free_cpumask_var(mask); + return restart_syscall(); + } + err = netif_set_xps_queue(dev, mask, index); + rtnl_unlock();
free_cpumask_var(mask);