This may happen on RUN -> SCAN -> RUN -> SCAN state transition:
1. RUN -> SCAN: in ieee80211_sta_join1(): iv_bss will be moved to obss,
refcnt will be reduced by 2 (default minimum).
Now, if old iv_bss have some extra references (for example, from
unacknowledged probe responses), it will not be freed and will stay
in the node table.
2. SCAN -> RUN.
3. If old iv_bss will not be deleted by the time when the next RUN -> SCAN
state transition occurs, then sta_leave() will reduce it's reference
counter once more. As a result, two last users will free it -> this will
lead to kernel panic.
In this patch old iv_bss entry is explicitly removed from the node table in
ieee80211_sta_join1() (as a result, it will not be processed by sta_leave()).
PR: kern/199676
Differential Revision: Andriy Voskoboinyk <s3erios@gmail.com>
8a0558317e