[PATCH v2] cfg80211: fix netdev registration deadlock
From: Johannes Berg <johannes@sipsolutions.net>
Date: 2021-02-01 18:24:32
Subsystem:
802.11 (including cfg80211/nl80211), the rest · Maintainers:
Johannes Berg, Linus Torvalds
From: Johannes Berg <redacted>
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: a05829a7222e ("cfg80211: avoid holding the RTNL when calling the driver")
Signed-off-by: Johannes Berg <redacted>
---
include/net/cfg80211.h | 4 +++-
net/wireless/core.c | 4 +++-
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 4741d71ead21..4cdd75449d73 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h@@ -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));
diff --git a/net/wireless/core.c b/net/wireless/core.c
index 18f9a5c214b5..a2785379df6e 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c@@ -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);
--
2.26.2