Fix accessing the __rcu pointer direct_functions with RCU protection.
Cc: [email protected]
Fixes: e93672f770d7 ("ftrace: Add update_ftrace_direct_mod function")
Signed-off-by: Leon Hwang <[email protected]>
---
kernel/trace/ftrace.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 9ea39110927f..414e425c2d80 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6617,6 +6617,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops,
struct ftrace_hash *hash, b
.func = ftrace_stub,
.flags = FTRACE_OPS_FL_STUB,
};
+ struct ftrace_hash *direct_hash;
struct ftrace_hash *orig_hash;
unsigned long size, i;
int err = -EINVAL;
@@ -6627,8 +6628,6 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops,
struct ftrace_hash *hash, b
return -EINVAL;
if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
return -EINVAL;
- if (direct_functions == EMPTY_HASH)
- return -EINVAL;
/*
* We can be called from within ops_func callback with direct_mutex
@@ -6636,6 +6635,12 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops,
struct ftrace_hash *hash, b
*/
if (do_direct_lock)
mutex_lock(&direct_mutex);
+ else
+ lockdep_assert_held_once(&direct_mutex);
+
+ direct_hash = rcu_dereference_protected(direct_functions,
lockdep_is_held(&direct_mutex));
+ if (direct_hash == EMPTY_HASH)
+ goto unlock;
orig_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL;
if (!orig_hash)
@@ -6667,7 +6672,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops,
struct ftrace_hash *hash, b
size = 1 << hash->size_bits;
for (i = 0; i < size; i++) {
hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
- tmp = __ftrace_lookup_ip(direct_functions, entry->ip);
+ tmp = __ftrace_lookup_ip(direct_hash, entry->ip);
if (!tmp)
continue;
tmp->direct = entry->direct;
--
2.55.0
