[PATCH 2/4] ftrace: Protect direct_functions in update_ftrace_direct_del
From: Leon Hwang <hidden>
Date: 2026-07-30 15:04:58
Also in:
lkml, stable
Subsystem:
function hooks (ftrace), the rest, tracing · Maintainers:
Steven Rostedt, Masami Hiramatsu, Linus Torvalds
Fix accessing the __rcu pointer direct_functions with RCU protection.
Cc: stable@vger.kernel.org
Fixes: 8d2c1233f371 ("ftrace: Add update_ftrace_direct_del function")
Signed-off-by: Leon Hwang <redacted>
---
kernel/trace/ftrace.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c5d1d0d42ccc..9ea39110927f 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c@@ -6512,6 +6512,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash) struct ftrace_hash *new_direct_functions; struct ftrace_hash *new_filter_hash = NULL; struct ftrace_hash *old_filter_hash; + struct ftrace_hash *direct_hash; struct ftrace_func_entry *entry; struct ftrace_func_entry *del; unsigned long size;
@@ -6523,11 +6524,13 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash) return -EINVAL; if (!(ops->flags & FTRACE_OPS_FL_ENABLED)) return -EINVAL; - if (direct_functions == EMPTY_HASH) - return -EINVAL; mutex_lock(&direct_mutex); + direct_hash = rcu_dereference_protected(direct_functions, lockdep_is_held(&direct_mutex)); + if (direct_hash == EMPTY_HASH) + goto out_unlock; + old_filter_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL; if (!hash_count(old_filter_hash))
@@ -6537,7 +6540,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash) size = 1 << hash->size_bits; for (int i = 0; i < size; i++) { hlist_for_each_entry(entry, &hash->buckets[i], hlist) { - del = __ftrace_lookup_ip(direct_functions, entry->ip); + del = __ftrace_lookup_ip(direct_hash, entry->ip); if (!del || del->direct != entry->direct) goto out_unlock; }
@@ -6548,7 +6551,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash) if (!new_filter_hash) goto out_unlock; - new_direct_functions = hash_sub(direct_functions, hash); + new_direct_functions = hash_sub(direct_hash, hash); if (!new_direct_functions) goto out_unlock;
@@ -6575,7 +6578,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash) /* free the new_direct_functions */ old_direct_functions = new_direct_functions; } else { - old_direct_functions = direct_functions; + old_direct_functions = direct_hash; rcu_assign_pointer(direct_functions, new_direct_functions); }
--
2.55.0