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

From: Steven Rostedt
Date: Thu Jul 13 2023 - 11:47:11 EST


From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>

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@xxxxxxxxxxx>
---
kernel/trace/trace.c | 40 ++++++++++++++++++++++++++++------------
1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 1c370ffbe062..3f38250637e2 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;
@@ -6709,7 +6723,12 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
}

trace_seq_init(&iter->seq);
- iter->trace = tr->current_trace;
+
+ iter->trace = kzalloc(sizeof(*iter->trace), GFP_KERNEL);
+ if (!iter->trace)
+ goto fail;
+
+ *iter->trace = *tr->current_trace;

if (!alloc_cpumask_var(&iter->started, GFP_KERNEL)) {
ret = -ENOMEM;
@@ -6763,10 +6782,7 @@ 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