From fe6a043c535acfec8f8e554536c87923dcb45097 Mon Sep 17 00:00:00 2001 From: Thomas Graf Date: Wed, 21 Jan 2015 11:54:01 +0000 Subject: [PATCH] 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: 97defe1ecf86 ("rhashtable: Per bucket locks & deferred expansion/shrinking") Reported-by: Ying Xue Signed-off-by: Thomas Graf Signed-off-by: David S. Miller --- lib/rhashtable.c | 24 +++++++++++++++--------- 1 file changed, 15 insertions(+), 9 deletions(-) diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 84a78e396a56..bc2d0d80d1f9 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -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); -- 2.20.1