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rhashtable: rhashtable_remove() must unlink in both tbl and future_tbl 

As removals can occur during resizes, entries may be referred to from
both tbl and future_tbl when the removal is requested. Therefore
rhashtable_remove() must unlink the entry in both tables if this is
the case. The existing code did search both tables but stopped when it
hit the first match.

Failing to unlink in both tables resulted in use after free.

Fixes: 97defe1ecf ("rhashtable: Per bucket locks & deferred expansion/shrinking")
Reported-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
hifive-unleashed-5.1
Thomas Graf 2015-01-21 11:54:01 +00:00 committed by David S. Miller
parent 1dc7b90f7c
commit fe6a043c53
1 changed files with 15 additions and 9 deletions
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24
lib/rhashtable.c
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@ -585,6 +585,7 @@ bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
struct rhash_head *he;
spinlock_t *lock;
unsigned int hash;
bool ret = false;
rcu_read_lock();
tbl = rht_dereference_rcu(ht->tbl, ht);
@ -602,17 +603,16 @@ restart:
}
rcu_assign_pointer(*pprev, obj->next);
atomic_dec(&ht->nelems);
spin_unlock_bh(lock);
rhashtable_wakeup_worker(ht);
rcu_read_unlock();
return true;
ret = true;
break;
}
/* The entry may be linked in either 'tbl', 'future_tbl', or both.
* 'future_tbl' only exists for a short period of time during
* resizing. Thus traversing both is fine and the added cost is
* very rare.
*/
if (tbl != rht_dereference_rcu(ht->future_tbl, ht)) {
spin_unlock_bh(lock);
@ -625,9 +625,15 @@ restart:
}
spin_unlock_bh(lock);
if (ret) {
atomic_dec(&ht->nelems);
rhashtable_wakeup_worker(ht);
}
rcu_read_unlock();
return false;
return ret;
}
EXPORT_SYMBOL_GPL(rhashtable_remove);