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netfilter: xt_hashlimit: fix race condition and simplify locking
As noticed by Shin Hong <hongshin@gmail.com>, there is a race between
htable_find_get() and htable_put():
htable_put(): htable_find_get():
spin_lock_bh(&hashlimit_lock);
<search entry>
atomic_dec_and_test(&hinfo->use)
atomic_inc(&hinfo->use)
spin_unlock_bh(&hashlimit_lock)
return hinfo;
spin_lock_bh(&hashlimit_lock);
hlist_del(&hinfo->node);
spin_unlock_bh(&hashlimit_lock);
htable_destroy(hinfo);
The entire locking concept is overly complicated, tables are only
created/referenced and released in process context, so a single
mutex works just fine. Remove the hashinfo_spinlock and atomic
reference count and use the mutex to protect table lookups/creation
and reference count changes.
Signed-off-by: Patrick McHardy <kaber@trash.net>