Commit c6ff5268 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller
Browse files

rhashtable: Fix walker list corruption

The commit ba7c95ea ("rhashtable:
Fix sleeping inside RCU critical section in walk_stop") introduced
a new spinlock for the walker list.  However, it did not convert
all existing users of the list over to the new spin lock.  Some
continued to use the old mutext for this purpose.  This obviously
led to corruption of the list.

The fix is to use the spin lock everywhere where we touch the list.

This also allows us to do rcu_rad_lock before we take the lock in
rhashtable_walk_start.  With the old mutex this would've deadlocked
but it's safe with the new spin lock.

Fixes: ba7c95ea

 ("rhashtable: Fix sleeping inside RCU...")
Reported-by: default avatarColin Ian King <colin.king@canonical.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3a324606
......@@ -518,10 +518,10 @@ int rhashtable_walk_init(struct rhashtable *ht, struct rhashtable_iter *iter)
if (!iter->walker)
return -ENOMEM;
mutex_lock(&ht->mutex);
spin_lock(&ht->lock);
iter->walker->tbl = rht_dereference(ht->tbl, ht);
list_add(&iter->walker->list, &iter->walker->tbl->walkers);
mutex_unlock(&ht->mutex);
spin_unlock(&ht->lock);
return 0;
}
......@@ -535,10 +535,10 @@ EXPORT_SYMBOL_GPL(rhashtable_walk_init);
*/
void rhashtable_walk_exit(struct rhashtable_iter *iter)
{
mutex_lock(&iter->ht->mutex);
spin_lock(&iter->ht->lock);
if (iter->walker->tbl)
list_del(&iter->walker->list);
mutex_unlock(&iter->ht->mutex);
spin_unlock(&iter->ht->lock);
kfree(iter->walker);
}
EXPORT_SYMBOL_GPL(rhashtable_walk_exit);
......@@ -562,14 +562,12 @@ int rhashtable_walk_start(struct rhashtable_iter *iter)
{
struct rhashtable *ht = iter->ht;
mutex_lock(&ht->mutex);
rcu_read_lock();
spin_lock(&ht->lock);
if (iter->walker->tbl)
list_del(&iter->walker->list);
rcu_read_lock();
mutex_unlock(&ht->mutex);
spin_unlock(&ht->lock);
if (!iter->walker->tbl) {
iter->walker->tbl = rht_dereference_rcu(ht->tbl, ht);
......
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