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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Johannes Berg <johannes@sipsolutions.net>,
        linux-wireless@vger.kernel.org
Cc:     Johannes Berg <johannes.berg@intel.com>
Subject: Re: [PATCH] cfg80211: fix race in netlink owner interface destruction
In-Reply-To: <20220201130951.22093-1-johannes@sipsolutions.net>
References: <20220201130951.22093-1-johannes@sipsolutions.net>
Date:   Tue, 01 Feb 2022 15:03:29 +0100
Message-ID: <87h79ielam.fsf@toke.dk>
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Johannes Berg <johannes@sipsolutions.net> writes:

> From: Johannes Berg <johannes.berg@intel.com>
>
> 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.
>
> Change-Id: Ie56cd0ef3f0d2108bb8a25c8bb5efced15e6a909
> Reported-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@redhat.com>
> Fixes: ea6b2098dd02 ("cfg80211: fix locking in netlink owner interface de=
struction")
> Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Looks like this fixed the crash I was seeing - thanks!

Tested-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@redhat.com>