linux-kernel - Re: [PATCH] trace: Avoid memory leak in predicate

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Date:   Tue, 28 May 2019 10:44:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tomas Bortoli <tomasbortoli@...il.com>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] trace: Avoid memory leak in predicate_parse()

On Tue, 28 May 2019 15:46:59 +0200
Tomas Bortoli <tomasbortoli@...il.com> wrote:

> In case of errors, predicate_parse() goes to the out_free label
> to free memory and to return an error code.
> 
> However, predicate_parse() does not free the predicates of the
> temporary prog_stack array, thence leaking them.
> 
> 
> Signed-off-by: Tomas Bortoli <tomasbortoli@...il.com>
> Reported-by: syzbot+6b8e0fb820e570c59e19@...kaller.appspotmail.com
> ---
>  kernel/trace/trace_events_filter.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index d3e59312ef40..98eafad750d3 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -433,6 +433,8 @@ predicate_parse(const char *str, int nr_parens, int nr_preds,
>  		parse_error(pe, -ENOMEM, 0);
>  		goto out_free;
>  	}
> +	memset(prog_stack, 0, nr_preds * sizeof(*prog_stack));
> +

Can you instead just switch the allocation of prog_stack to use
kcalloc()?

Thanks,

-- Steve


>  	inverts = kmalloc_array(nr_preds, sizeof(*inverts), GFP_KERNEL);
>  	if (!inverts) {
>  		parse_error(pe, -ENOMEM, 0);
> @@ -579,6 +581,8 @@ predicate_parse(const char *str, int nr_parens, int nr_preds,
>  out_free:
>  	kfree(op_stack);
>  	kfree(inverts);
> +	for (i = 0; prog_stack[i].pred; i++)
> +		kfree(prog_stack[i].pred);
>  	kfree(prog_stack);
>  	return ERR_PTR(ret);
>  }