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Merge branch 'rhashtable-fixes-next'

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Herbert Xu says:

====================
rhashtable: Fix two bugs caused by multiple rehash preparation

While testing some new patches over the weekend I discovered a
couple of bugs in the series that had just been merged.  These
two patches fix them:

1) A use-after-free in the walker that can cause crashes when
walking during a rehash.

2) When a second rehash starts during a single rhashtable_remove
call the remove may fail when it shouldn't.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2015-03-15 22:22:17 -04:00
commit 7993d44ea1
1 changed files with 11 additions and 13 deletions
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24
lib/rhashtable.c
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@ -511,28 +511,25 @@ static bool __rhashtable_remove(struct rhashtable *ht,
*/
bool rhashtable_remove(struct rhashtable *ht, struct rhash_head *obj)
{
struct bucket_table *tbl, *old_tbl;
struct bucket_table *tbl;
bool ret;
rcu_read_lock();
old_tbl = rht_dereference_rcu(ht->tbl, ht);
ret = __rhashtable_remove(ht, old_tbl, obj);
tbl = rht_dereference_rcu(ht->tbl, ht);
/* Because we have already taken (and released) the bucket
* lock in old_tbl, if we find that future_tbl is not yet
* visible then that guarantees the entry to still be in
* old_tbl if it exists.
* the old tbl if it exists.
*/
tbl = rht_dereference_rcu(old_tbl->future_tbl, ht) ?: old_tbl;
if (!ret && old_tbl != tbl)
ret = __rhashtable_remove(ht, tbl, obj);
while (!(ret = __rhashtable_remove(ht, tbl, obj)) &&
(tbl = rht_dereference_rcu(tbl->future_tbl, ht)))
;
if (ret) {
bool no_resize_running = tbl == old_tbl;
atomic_dec(&ht->nelems);
if (no_resize_running && rht_shrink_below_30(ht, tbl))
if (rht_shrink_below_30(ht, tbl))
schedule_work(&ht->run_work);
}
@ -854,10 +851,8 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter)
struct rhashtable *ht;
struct bucket_table *tbl = iter->walker->tbl;
rcu_read_unlock();
if (!tbl)
return;
goto out;
ht = iter->ht;
@ -869,6 +864,9 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter)
mutex_unlock(&ht->mutex);
iter->p = NULL;
out:
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(rhashtable_walk_stop);