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 EB7A4C433F5 for ; Fri, 22 Apr 2022 15:13:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1449306AbiDVPQS (ORCPT ); Fri, 22 Apr 2022 11:16:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1449292AbiDVPQN (ORCPT ); Fri, 22 Apr 2022 11:16:13 -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 AAC915D5F4 for ; Fri, 22 Apr 2022 08:13:19 -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 68F24B830D7 for ; Fri, 22 Apr 2022 15:13:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 087C3C385A8; Fri, 22 Apr 2022 15:13:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650640397; bh=dlhnkGIAETkf0PM+DA9mEiVM6qZtwnjdx+JDhH9WBps=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=p57lLgFnDbw+D3ySDZ70CYRAge4zheEOlHuaX4q4jENTDFH1xl3w7k888nfcZTAon 4/HRucBXiRebcis3ku61yB395F2HmY4Vra91RqTdz2fq9wO2COxonY0+tWtnEwao0Z cesjM7VtwcyGfpqt4QFOE+z+plhD21byUPgYWPqs2wWn5FzoAZZJJZ2YgqkxZTi+Kx n6hJ/dCmb2WXJcfsVNxC4IQp5GOOvaGXq/dBYkQFY/7/3i9HjgWnxV7AwdvLfEmSUm n/RcBaQ26ZAOu+a0cWt3mKpx+ZFW7el2nFc9MG4qmmhrX88MHtfDks5unu7OpoTvWl HYC2HP22HWbYA== Date: Sat, 23 Apr 2022 00:13:11 +0900 From: Masami Hiramatsu To: Keita Suzuki Cc: mhiramat@kernel.org, Steven Rostedt , Ingo Molnar , linux-kernel@vger.kernel.org, Tom Zanussi , Tom Zanussi Subject: Re: [PATCH] tracing: Fix potential double free in create_var_ref() Message-Id: <20220423001311.31e2dff59708ddd3043e55af@kernel.org> In-Reply-To: <20220422060025.1436075-1-keitasuzuki.park@sslab.ics.keio.ac.jp> References: <20220422060025.1436075-1-keitasuzuki.park@sslab.ics.keio.ac.jp> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; 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: linux-kernel@vger.kernel.org Hi Keita, On Fri, 22 Apr 2022 06:00:25 +0000 Keita Suzuki wrote: > In create_var_ref(), init_var_ref() is called to initialize the fields > of variable ref_field, which is allocated in the previous function call > to create_hist_field(). Function init_var_ref() allocates the > corresponding fields such as ref_field->system, but frees these fields > when the function encounters an error. The caller later calls > destroy_hist_field() to conduct error handling, which frees the fields > and the variable itself. This results in double free of the fields which > are already freed in the previous function. > > Fix this by storing NULL to the corresponding fields when they are freed > in init_var_ref(). > Good catch! this looks good to me. Reviewed-by: Masami Hiramatsu BTW, could you Cc the original code authoer and if you fix a bug and add Fixes: tag? That will help the original author can check the bug and help stable kernel maintainers to pick the patch. :) To find the original commit, you can use the 'git blame'. $ git blame kernel/trace/trace_events_hist.c -L 2093,2100 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2093) return err; 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2094) free: 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2095) kfree(ref_field->system); 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2096) kfree(ref_field->event_name); 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2097) kfree(ref_field->name); 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2098) 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2099) goto out; 067fe038e70f6 (Tom Zanussi 2018-01-15 20:51:56 -0600 2100) } Then, git show will tell you the original author. $ git show 067fe038e70f6 And get the format of the commit for Fixes tag. $ git --no-pager show -s --abbrev-commit --abbrev=12 --pretty=format:"%h (\"%s\")%n" 067fe038e70f6 067fe038e70f ("tracing: Add variable reference handling to hist triggers") Then you can add lines like: Fixes: 067fe038e70f ("tracing: Add variable reference handling to hist triggers") Cc: stable@vger.kernel.org Thank you, > Signed-off-by: Keita Suzuki > --- > kernel/trace/trace_events_hist.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > index 44db5ba9cabb..a0e41906d9ce 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -2093,8 +2093,11 @@ static int init_var_ref(struct hist_field *ref_field, > return err; > free: > kfree(ref_field->system); > + ref_field->system = NULL; > kfree(ref_field->event_name); > + ref_field->event_name = NULL; > kfree(ref_field->name); > + ref_field->name = NULL; > > goto out; > } > -- > 2.25.1 > -- Masami Hiramatsu