| Message ID | 20201223212323.3603139-4-atenart@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | net-sysfs: fix race conditions in the xps code | expand |
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c index 65886bfbf822..62ca2f2c0ee6 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -1499,10 +1499,17 @@ static ssize_t xps_rxqs_store(struct netdev_queue *queue, const char *buf, return err; } + if (!rtnl_trylock()) { + bitmap_free(mask); + return restart_syscall(); + } + cpus_read_lock(); err = __netif_set_xps_queue(dev, mask, index, true); cpus_read_unlock(); + rtnl_unlock(); + bitmap_free(mask); return err ? : len; }
Two race conditions can be triggered when storing xps rxqs, 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_rxqs 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_rxqs_store. Fixes: 8af2c06ff4b1 ("net-sysfs: Add interface for Rx queue(s) map per Tx queue") Signed-off-by: Antoine Tenart <atenart@kernel.org> --- net/core/net-sysfs.c | 7 +++++++ 1 file changed, 7 insertions(+)