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SubjectRe: [PATCH v2] tracing: Fix possible memory leak in __create_synth_event
On Thu,  9 Dec 2021 02:43:17 +0000
Miaoqian Lin <linmq006@gmail.com> wrote:

> Before goto err, call argv_free to handle argv in order to prevent
> memory leak.

No. That's what you did previously. This patch does:

There's error paths in __create_synth_event() after the argv is allocated
that fail to free it. Add a jump to free it when necessary.

>
> Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
> Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> ---
> Changes in v2:
> use a cleaner way to handle cleanup operations
> ---
> ---
> kernel/trace/trace_events_synth.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> index 22db3ce95e74..c4a490ec7a38 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -1262,26 +1262,26 @@ static int __create_synth_event(const char *name, const char *raw_fields)

You failed to add:

if (IS_ERR(field)) {
- argv_free(argv);
ret = PTR_ERR(field);
- goto err;
+ goto err_free_arg;
}


> if (cmd_version > 1 && n_fields_this_loop >= 1) {
> synth_err(SYNTH_ERR_INVALID_CMD, errpos(field_str));
> ret = -EINVAL;
> - goto err;
> + goto err_free_arg;
> }
>
> fields[n_fields++] = field;
> if (n_fields == SYNTH_FIELDS_MAX) {
> synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
> ret = -EINVAL;
> - goto err;
> + goto err_free_arg;
> }
>
> n_fields_this_loop++;
> }
>

No space here.

> + argv_free(argv);

And a space here.

If you had just applied the patch I gave you, you would not have had these
mistakes.

Anyway, I'll update your patch and start testing it. No need to send
another patch.

-- Steve

> if (consumed < argc) {
> synth_err(SYNTH_ERR_INVALID_CMD, 0);
> ret = -EINVAL;
> goto err;
> }
>
> - argv_free(argv);
> }
>
> if (n_fields == 0) {
> @@ -1307,6 +1307,8 @@ static int __create_synth_event(const char *name, const char *raw_fields)
> kfree(saved_fields);
>
> return ret;
> + err_free_arg:
> + argv_free(argv);
> err:
> for (i = 0; i < n_fields; i++)
> free_synth_field(fields[i]);

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