| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.19 23/77] net-sysfs: take the rtnl lock when storing xps_cpus | Date | Mon, 11 Jan 2021 14:01:32 +0100 |
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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 @@ -1323,7 +1323,13 @@ 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);
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