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Subject[PATCH 4.19 76/81] ftrace: Get a reference counter for the trace_array on filter files
Date
From: Steven Rostedt (VMware) <rostedt@goodmis.org>

commit 9ef16693aff8137faa21d16ffe65bb9832d24d71 upstream.

The ftrace set_ftrace_filter and set_ftrace_notrace files are specific for
an instance now. They need to take a reference to the instance otherwise
there could be a race between accessing the files and deleting the instance.

It wasn't until the :mod: caching where these file operations started
referencing the trace_array directly.

Cc: stable@vger.kernel.org
Fixes: 673feb9d76ab3 ("ftrace: Add :mod: caching infrastructure to trace_array")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/trace/ftrace.c | 27 ++++++++++++++++++---------
1 file changed, 18 insertions(+), 9 deletions(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3557,21 +3557,22 @@ ftrace_regex_open(struct ftrace_ops *ops
struct ftrace_hash *hash;
struct list_head *mod_head;
struct trace_array *tr = ops->private;
- int ret = 0;
+ int ret = -ENOMEM;

ftrace_ops_init(ops);

if (unlikely(ftrace_disabled))
return -ENODEV;

+ if (tr && trace_array_get(tr) < 0)
+ return -ENODEV;
+
iter = kzalloc(sizeof(*iter), GFP_KERNEL);
if (!iter)
- return -ENOMEM;
+ goto out;

- if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX)) {
- kfree(iter);
- return -ENOMEM;
- }
+ if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX))
+ goto out;

iter->ops = ops;
iter->flags = flag;
@@ -3601,13 +3602,13 @@ ftrace_regex_open(struct ftrace_ops *ops

if (!iter->hash) {
trace_parser_put(&iter->parser);
- kfree(iter);
- ret = -ENOMEM;
goto out_unlock;
}
} else
iter->hash = hash;

+ ret = 0;
+
if (file->f_mode & FMODE_READ) {
iter->pg = ftrace_pages_start;

@@ -3619,7 +3620,6 @@ ftrace_regex_open(struct ftrace_ops *ops
/* Failed */
free_ftrace_hash(iter->hash);
trace_parser_put(&iter->parser);
- kfree(iter);
}
} else
file->private_data = iter;
@@ -3627,6 +3627,13 @@ ftrace_regex_open(struct ftrace_ops *ops
out_unlock:
mutex_unlock(&ops->func_hash->regex_lock);

+ out:
+ if (ret) {
+ kfree(iter);
+ if (tr)
+ trace_array_put(tr);
+ }
+
return ret;
}

@@ -5024,6 +5031,8 @@ int ftrace_regex_release(struct inode *i

mutex_unlock(&iter->ops->func_hash->regex_lock);
free_ftrace_hash(iter->hash);
+ if (iter->tr)
+ trace_array_put(iter->tr);
kfree(iter);

return 0;

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