On Tue, 17 May 2022 17:57:23 +0800 Yuanjun Gong <ruc_gongyuanjun@xxxxxxx> wrote: > From: Gong Yuanjun <ruc_gongyuanjun@xxxxxxx> > > In hist_trigger_elt_data_alloc(), elt_data is freed by > hist_elt_data_free() if kcalloc fails. > > static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt) > { > ... > elt_data->field_var_str = kcalloc(n_str, sizeof(char *), GFP_KERNEL); > if (!elt_data->field_var_str) { But at this position elt_data->n_field_var_str is zero. > hist_elt_data_free(elt_data); > return -EINVAL; > } > ...} > > In hist_elt_data_free() the elt_data->field_var_str field should be > checked before dereference. > > Signed-off-by: Gong Yuanjun <ruc_gongyuanjun@xxxxxxx> > --- > kernel/trace/trace_events_hist.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > index 44db5ba9cabb..73177c9f94b2 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -1576,11 +1576,11 @@ static void hist_elt_data_free(struct hist_elt_data *elt_data) > { > unsigned int i; > > - for (i = 0; i < elt_data->n_field_var_str; i++) This loop will not execute because n_field_var_str is zero, and 0 < 0 is false. > - kfree(elt_data->field_var_str[i]); > - > - kfree(elt_data->field_var_str); freeing a NULL pointer is OK to do. There is nothing wrong with the current code. NACK. -- Steve > - > + if (elt_data->field_var_str) { > + for (i = 0; i < elt_data->n_field_var_str; i++) > + kfree(elt_data->field_var_str[i]); > + kfree(elt_data->field_var_str); > + } > kfree(elt_data->comm); > kfree(elt_data); > }