Re: [PATCH] trace: Avoid memory leak in predicate_parse()

[Steven Rostedt]

On Tue, 28 May 2019 15:46:59 +0200
Tomas Bortoli <tomasbort...@gmail.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 <tomasbort...@gmail.com>
> Reported-by: syzbot+6b8e0fb820e570c59...@syzkaller.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);
>  }