From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACD2CC433EF for ; Wed, 18 May 2022 19:28:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241805AbiERT2q (ORCPT ); Wed, 18 May 2022 15:28:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44126 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232246AbiERT2q (ORCPT ); Wed, 18 May 2022 15:28:46 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 988A71BA8E6; Wed, 18 May 2022 12:28:44 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4AA72B821AB; Wed, 18 May 2022 19:28:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72D9FC385A5; Wed, 18 May 2022 19:28:41 +0000 (UTC) Date: Wed, 18 May 2022 15:28:39 -0400 From: Steven Rostedt To: Yuanjun Gong Cc: Ingo Molnar , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/1] tracing: fix possible null pointer dereference Message-ID: <20220518152839.0f51830b@gandalf.local.home> In-Reply-To: <20220517095723.7426-1-ruc_gongyuanjun@163.com> References: <20220517095723.7426-1-ruc_gongyuanjun@163.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Tue, 17 May 2022 17:57:23 +0800 Yuanjun Gong wrote: > From: Gong Yuanjun > > 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 > --- > 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); > }