[PATCH v2 2/2] tracing: Add free_trace_iter_content() helper function

Steven Rostedt
2023-07-15T14:14:04Z

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

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.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 33 ++++++++++++++++++++++-----------
1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1c370ffbe062..8775930aa545 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4815,6 +4815,25 @@ 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)
{
@@ -4922,8 +4941,7 @@ __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);
@@ -5002,11 +5020,7 @@ 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;
@@ -6763,10 +6777,7 @@ 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);
--
2.40.1