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cfg80211: fix netdev registration deadlock 

If register_netdevice() fails after having called cfg80211's
netdev notifier (cfg80211_netdev_notifier_call) it will call
the notifier again with UNREGISTER. This would then lock the
wiphy mutex because we're marked as registered, which causes
a deadlock.

Fix this by separately keeping track of whether or not we're
in the middle of registering to also skip the notifier call
on this unregister.

Reported-by: syzbot+2ae0ca9d7737ad1a62b7@syzkaller.appspotmail.com
Fixes: a05829a722 ("cfg80211: avoid holding the RTNL when calling the driver")
Link: https://lore.kernel.org/r/20210201192048.ed8bad436737.I7cae042c44b15f80919a285799a15df467e9d42d@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
master
Johannes Berg 2021-02-01 19:20:50 +01:00
parent 776a39b819
commit 40c575d1ec
2 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/net/cfg80211.h
View File

@ -5299,6 +5299,8 @@ static inline void wiphy_unlock(struct wiphy *wiphy)
* @wiphy: pointer to hardware description
* @iftype: interface type
* @registered: is this wdev already registered with cfg80211
* @registering: indicates we're doing registration under wiphy lock
* for the notifier
* @list: (private) Used to collect the interfaces
* @netdev: (private) Used to reference back to the netdev, may be %NULL
* @identifier: (private) Identifier used in nl80211 to identify this
@ -5382,7 +5384,7 @@ struct wireless_dev {
struct mutex mtx;
bool use_4addr, is_running, registered;
bool use_4addr, is_running, registered, registering;
u8 address[ETH_ALEN] __aligned(sizeof(u16));

4
net/wireless/core.c
View File

@ -1346,6 +1346,7 @@ int cfg80211_register_netdevice(struct net_device *dev)
/* we'll take care of this */
wdev->registered = true;
wdev->registering = true;
ret = register_netdevice(dev);
if (ret)
goto out;
@ -1361,6 +1362,7 @@ int cfg80211_register_netdevice(struct net_device *dev)
cfg80211_register_wdev(rdev, wdev);
ret = 0;
out:
wdev->registering = false;
if (ret)
wdev->registered = false;
return ret;
@ -1403,7 +1405,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
* It is possible to get NETDEV_UNREGISTER multiple times,
* so check wdev->registered.
*/
if (wdev->registered) {
if (wdev->registered && !wdev->registering) {
wiphy_lock(&rdev->wiphy);
_cfg80211_unregister_wdev(wdev, false);
wiphy_unlock(&rdev->wiphy);