tracing: Add free_trace_iter_content() helper function

As the trace iterator is created and used by various interfaces, the clean
up of it needs to be consistent. Create a free_trace_iter_content() helper
function that frees the content of the iterator and use that to clean it
up in all places that it is used.

Link: https://lkml.kernel.org/r/20230715141348.341887497@goodmis.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5e665c3..a3c4f98 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4799,6 +4799,25 @@ static const struct seq_operations tracer_seq_ops = {
        .show           = s_show,
 };
 
+/*
+ * Note, as iter itself can be allocated and freed in different
+ * ways, this function is only used to free its content, and not
+ * the iterator itself. The only requirement to all the allocations
+ * is that it must zero all fields (kzalloc), as freeing works with
+ * ethier allocated content or NULL.
+ */
+static void free_trace_iter_content(struct trace_iterator *iter)
+{
+       /* The fmt is either NULL, allocated or points to static_fmt_buf */
+       if (iter->fmt != static_fmt_buf)
+               kfree(iter->fmt);
+
+       kfree(iter->temp);
+       kfree(iter->buffer_iter);
+       mutex_destroy(&iter->mutex);
+       free_cpumask_var(iter->started);
+}
+
 static struct trace_iterator *
 __tracing_open(struct inode *inode, struct file *file, bool snapshot)
 {
@@ -4906,8 +4925,7 @@ __tracing_open(struct inode *inode, struct file *file, bool snapshot)
 
  fail:
        mutex_unlock(&trace_types_lock);
-       kfree(iter->temp);
-       kfree(iter->buffer_iter);
+       free_trace_iter_content(iter);
 release:
        seq_release_private(inode, file);
        return ERR_PTR(-ENOMEM);
@@ -4986,11 +5004,7 @@ static int tracing_release(struct inode *inode, struct file *file)
 
        mutex_unlock(&trace_types_lock);
 
-       mutex_destroy(&iter->mutex);
-       free_cpumask_var(iter->started);
-       kfree(iter->fmt);
-       kfree(iter->temp);
-       kfree(iter->buffer_iter);
+       free_trace_iter_content(iter);
        seq_release_private(inode, file);
 
        return 0;
@@ -6747,10 +6761,7 @@ static int tracing_release_pipe(struct inode *inode, struct file *file)
 
        mutex_unlock(&trace_types_lock);
 
-       free_cpumask_var(iter->started);
-       kfree(iter->fmt);
-       kfree(iter->temp);
-       mutex_destroy(&iter->mutex);
+       free_trace_iter_content(iter);
        kfree(iter);
 
        trace_array_put(tr);