Commit ba7c95ea authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller

rhashtable: Fix sleeping inside RCU critical section in walk_stop

The commit 963ecbd4 ("rhashtable:
Fix use-after-free in rhashtable_walk_stop") fixed a real bug
but created another one because we may end up sleeping inside an
RCU critical section.

This patch fixes it properly by replacing the mutex with a spin
lock that specifically protects the walker lists.
Reported-by: default avatarSasha Levin <>
Signed-off-by: default avatarHerbert Xu <>
Signed-off-by: default avatarDavid S. Miller <>
parent ce046c56
......@@ -133,6 +133,7 @@ struct rhashtable_params {
* @p: Configuration parameters
* @run_work: Deferred worker to expand/shrink asynchronously
* @mutex: Mutex to protect current/future table swapping
* @lock: Spin lock to protect walker list
* @being_destroyed: True if table is set up for destruction
struct rhashtable {
......@@ -144,6 +145,7 @@ struct rhashtable {
struct rhashtable_params p;
struct work_struct run_work;
struct mutex mutex;
spinlock_t lock;
......@@ -256,8 +256,10 @@ static int rhashtable_rehash_table(struct rhashtable *ht)
/* Publish the new table pointer. */
rcu_assign_pointer(ht->tbl, new_tbl);
list_for_each_entry(walker, &old_tbl->walkers, list)
walker->tbl = NULL;
/* Wait for readers. All new readers will see the new
* table, and thus no references to the old table will
......@@ -635,12 +637,12 @@ void rhashtable_walk_stop(struct rhashtable_iter *iter)
ht = iter->ht;
if (tbl->rehash < tbl->size)
list_add(&iter->walker->list, &tbl->walkers);
iter->walker->tbl = NULL;
iter->p = NULL;
......@@ -723,6 +725,7 @@ int rhashtable_init(struct rhashtable *ht,
memset(ht, 0, sizeof(*ht));
memcpy(&ht->p, params, sizeof(*params));
if (params->min_size)
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