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authorJohannes Berg <johannes.berg@intel.com>2021-05-17 16:03:23 +0200
committerJohannes Berg <johannes.berg@intel.com>2021-06-08 11:33:07 +0200
commitd5befb224edbe53056c2c18999d630dafb4a08b9 (patch)
treed02b071713fea8c3df26ce8ac33dd05c9695b9d1
parentbddc0c411a45d3718ac535a070f349be8eca8d48 (diff)
mac80211: fix deadlock in AP/VLAN handling
Syzbot reports that when you have AP_VLAN interfaces that are up and close the AP interface they belong to, we get a deadlock. No surprise - since we dev_close() them with the wiphy mutex held, which goes back into the netdev notifier in cfg80211 and tries to acquire the wiphy mutex there. To fix this, we need to do two things: 1) prevent changing iftype while AP_VLANs are up, we can't easily fix this case since cfg80211 already calls us with the wiphy mutex held, but change_interface() is relatively rare in drivers anyway, so changing iftype isn't used much (and userspace has to fall back to down/change/up anyway) 2) pull the dev_close() loop over VLANs out of the wiphy mutex section in the normal stop case Cc: stable@vger.kernel.org Reported-by: syzbot+452ea4fbbef700ff0a56@syzkaller.appspotmail.com Fixes: a05829a7222e ("cfg80211: avoid holding the RTNL when calling the driver") Link: https://lore.kernel.org/r/20210517160322.9b8f356c0222.I392cb0e2fa5a1a94cf2e637555d702c7e512c1ff@changeid Signed-off-by: Johannes Berg <johannes.berg@intel.com>
-rw-r--r--net/mac80211/iface.c19
1 files changed, 12 insertions, 7 deletions
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 2e2f73a4aa73..137fa4c50e07 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -476,14 +476,7 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata, bool going_do
GFP_KERNEL);
}
- /* APs need special treatment */
if (sdata->vif.type == NL80211_IFTYPE_AP) {
- struct ieee80211_sub_if_data *vlan, *tmpsdata;
-
- /* down all dependent devices, that is VLANs */
- list_for_each_entry_safe(vlan, tmpsdata, &sdata->u.ap.vlans,
- u.vlan.list)
- dev_close(vlan->dev);
WARN_ON(!list_empty(&sdata->u.ap.vlans));
} else if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN) {
/* remove all packets in parent bc_buf pointing to this dev */
@@ -641,6 +634,15 @@ static int ieee80211_stop(struct net_device *dev)
{
struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+ /* close all dependent VLAN interfaces before locking wiphy */
+ if (sdata->vif.type == NL80211_IFTYPE_AP) {
+ struct ieee80211_sub_if_data *vlan, *tmpsdata;
+
+ list_for_each_entry_safe(vlan, tmpsdata, &sdata->u.ap.vlans,
+ u.vlan.list)
+ dev_close(vlan->dev);
+ }
+
wiphy_lock(sdata->local->hw.wiphy);
ieee80211_do_stop(sdata, true);
wiphy_unlock(sdata->local->hw.wiphy);
@@ -1591,6 +1593,9 @@ static int ieee80211_runtime_change_iftype(struct ieee80211_sub_if_data *sdata,
switch (sdata->vif.type) {
case NL80211_IFTYPE_AP:
+ if (!list_empty(&sdata->u.ap.vlans))
+ return -EBUSY;
+ break;
case NL80211_IFTYPE_STATION:
case NL80211_IFTYPE_ADHOC:
case NL80211_IFTYPE_OCB: