dev_put allows a device to be freed when all its references are dropped. After that we are not allowed to access that information anymore. Access to the data structure of a net_device must be surrounded a dev_hold and ended using dev_put.
batman-adv adds a device to its own management structure in hardif_add_interface and will release it in hardif_remove_interface. Thus it must hold a reference all the time between those functions to prevent any access to the already released net_device structure. Reported-by: Tim Glaremin <[email protected]> Signed-off-by: Sven Eckelmann <[email protected]> --- batman-adv/hard-interface.c | 10 ++++++---- 1 files changed, 6 insertions(+), 4 deletions(-) diff --git a/batman-adv/hard-interface.c b/batman-adv/hard-interface.c index a141ffb..2025ba1 100644 --- a/batman-adv/hard-interface.c +++ b/batman-adv/hard-interface.c @@ -213,7 +213,6 @@ static void hardif_activate_interface(struct batman_if *batman_if) return; bat_priv = netdev_priv(batman_if->soft_iface); - dev_hold(batman_if->net_dev); update_mac_addresses(batman_if); batman_if->if_status = IF_TO_BE_ACTIVATED; @@ -238,8 +237,6 @@ static void hardif_deactivate_interface(struct batman_if *batman_if) (batman_if->if_status != IF_TO_BE_ACTIVATED)) return; - dev_put(batman_if->net_dev); - batman_if->if_status = IF_INACTIVE; bat_info(batman_if->soft_iface, "Interface deactivated: %s\n", @@ -385,11 +382,13 @@ static struct batman_if *hardif_add_interface(struct net_device *net_dev) if (ret != 1) goto out; + dev_hold(net_dev); + batman_if = kmalloc(sizeof(struct batman_if), GFP_ATOMIC); if (!batman_if) { pr_err("Can't add interface (%s): out of memory\n", net_dev->name); - goto out; + goto release_dev; } ret = sysfs_add_hardif(&batman_if->hardif_obj, net_dev); @@ -408,6 +407,8 @@ static struct batman_if *hardif_add_interface(struct net_device *net_dev) free_if: kfree(batman_if); +release_dev: + dev_put(net_dev); out: return NULL; } @@ -431,6 +432,7 @@ static void hardif_remove_interface(struct batman_if *batman_if) batman_if->if_status = IF_TO_BE_REMOVED; list_del_rcu(&batman_if->list); sysfs_del_hardif(&batman_if->hardif_obj); + dev_put(batman_if->net_dev); call_rcu(&batman_if->rcu, hardif_free_interface); } -- 1.7.1
