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cfg80211: fix race in netlink owner interface destruction

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My previous fix here to fix the deadlock left a race where
the exact same deadlock (see the original commit referenced
below) can still happen if cfg80211_destroy_ifaces() already
runs while nl80211_netlink_notify() is still marking some
interfaces as nl_owner_dead.

The race happens because we have two loops here - first we
dev_close() all the netdevs, and then we destroy them. If we
also have two netdevs (first one need only be a wdev though)
then we can find one during the first iteration, close it,
and go to the second iteration -- but then find two, and try
to destroy also the one we didn't close yet.

Fix this by only iterating once.

Reported-by: Toke Høiland-Jørgensen <toke@redhat.com>
Fixes: ea6b2098dd02 ("cfg80211: fix locking in netlink owner interface destruction")
Tested-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20220201130951.22093-1-johannes@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Johannes Berg 2022-02-01 14:09:51 +01:00
parent 5f06f6bf8d
commit f0a6fd1527
1 changed files with 4 additions and 13 deletions
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17
net/wireless/core.c
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@ -5,7 +5,7 @@
* Copyright 2006-2010 Johannes Berg <johannes@sipsolutions.net>
* Copyright 2013-2014 Intel Mobile Communications GmbH
* Copyright 2015-2017 Intel Deutschland GmbH
* Copyright (C) 2018-2021 Intel Corporation
* Copyright (C) 2018-2022 Intel Corporation
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
@ -332,29 +332,20 @@ static void cfg80211_event_work(struct work_struct *work)
void cfg80211_destroy_ifaces(struct cfg80211_registered_device *rdev)
{
struct wireless_dev *wdev, *tmp;
bool found = false;
ASSERT_RTNL();
list_for_each_entry(wdev, &rdev->wiphy.wdev_list, list) {
list_for_each_entry_safe(wdev, tmp, &rdev->wiphy.wdev_list, list) {
if (wdev->nl_owner_dead) {
if (wdev->netdev)
dev_close(wdev->netdev);
found = true;
}
}
if (!found)
return;
wiphy_lock(&rdev->wiphy);
list_for_each_entry_safe(wdev, tmp, &rdev->wiphy.wdev_list, list) {
if (wdev->nl_owner_dead) {
wiphy_lock(&rdev->wiphy);
cfg80211_leave(rdev, wdev);
rdev_del_virtual_intf(rdev, wdev);
wiphy_unlock(&rdev->wiphy);
}
}
wiphy_unlock(&rdev->wiphy);
}
static void cfg80211_destroy_iface_wk(struct work_struct *work)