ftrace: Reinitialize hash to EMPTY_HASH after freeing

There's several locations that free a ftrace hash pointer but may be
referenced again. Reset them to EMPTY_HASH so that a u-a-f bug doesn't
happen.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250417110933.20ab718b@gandalf.local.home
Fixes: 0ae6b8ce200d ("ftrace: Fix accounting of subop hashes")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 43394445390cd95d3e3c1a784ca1f94ddd23374b..d0e4a902bb4028222fdb88fc09dbaaaff8eb1d0a 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1297,6 +1297,8 @@ void ftrace_free_filter(struct ftrace_ops *ops)
                return;
        free_ftrace_hash(ops->func_hash->filter_hash);
        free_ftrace_hash(ops->func_hash->notrace_hash);
+       ops->func_hash->filter_hash = EMPTY_HASH;
+       ops->func_hash->notrace_hash = EMPTY_HASH;
 }
 EXPORT_SYMBOL_GPL(ftrace_free_filter);
 
@@ -3443,6 +3445,7 @@ static int add_next_hash(struct ftrace_hash **filter_hash, struct ftrace_hash **
                                  size_bits);
                if (ret < 0) {
                        free_ftrace_hash(*filter_hash);
+                       *filter_hash = EMPTY_HASH;
                        return ret;
                }
        }
@@ -3472,6 +3475,7 @@ static int add_next_hash(struct ftrace_hash **filter_hash, struct ftrace_hash **
                                     subops_hash->notrace_hash);
                if (ret < 0) {
                        free_ftrace_hash(*notrace_hash);
+                       *notrace_hash = EMPTY_HASH;
                        return ret;
                }
        }