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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4B1F0C433EF for ; Wed, 17 Nov 2021 03:47:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1B1D76126A for ; Wed, 17 Nov 2021 03:47:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232755AbhKQDuF (ORCPT ); Tue, 16 Nov 2021 22:50:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:48894 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229614AbhKQDuE (ORCPT ); Tue, 16 Nov 2021 22:50:04 -0500 Received: from rorschach.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B58E5619EA; Wed, 17 Nov 2021 03:47:05 +0000 (UTC) Date: Tue, 16 Nov 2021 22:47:03 -0500 From: Steven Rostedt To: Kalesh Singh Cc: kernel-team@android.com, mhiramat@kernel.org, zanussi@kernel.org, kernel test robot , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH] tracing/histogram: Fix UAF in destroy_hist_field() Message-ID: <20211116224703.133f1750@rorschach.local.home> In-Reply-To: <20211117021223.2137117-1-kaleshsingh@google.com> References: <20211117021223.2137117-1-kaleshsingh@google.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: linux-kernel@vger.kernel.org On Tue, 16 Nov 2021 18:12:22 -0800 Kalesh Singh wrote: > Calling destroy_hist_field() on an expression will recursively free > any operands associated with the expression. If during expression > parsing the operands of the expression are already set when an error > is encountered, there is no need to explicity free the operands. Doing > so will result in destroy_hist_field() being called twice for the > operands and lead to a use-after-free (UAF) error. > > Fix this by only calling destroy_hist_field() for the expression if the > operands are already set. > > Signed-off-by: Kalesh Singh > Fixes: 8b5d46fd7a38 ("tracing/histogram: Optimize division by constants") > Reported-by: kernel test robot > --- > kernel/trace/trace_events_hist.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c > index 5ea2c9ec54a6..e3856eaf2ac3 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -2669,7 +2669,7 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, > if (!divisor) { > hist_err(file->tr, HIST_ERR_DIVISION_BY_ZERO, errpos(str)); > ret = -EDOM; > - goto free; > + goto free_expr; > } > > /* > @@ -2709,7 +2709,7 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, > expr->type = kstrdup_const(operand1->type, GFP_KERNEL); > if (!expr->type) { > ret = -ENOMEM; > - goto free; > + goto free_expr; > } > > expr->name = expr_str(expr, 0); > @@ -2719,6 +2719,7 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, > free: > destroy_hist_field(operand1, 0); > destroy_hist_field(operand2, 0); > +free_expr: > destroy_hist_field(expr, 0); > > return ERR_PTR(ret); > > base-commit: 8ab774587903771821b59471cc723bba6d893942 Wouldn't this be a simpler and more robust fix? diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 5ea2c9ec54a6..aab69b4ffe11 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -2717,8 +2717,10 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, return expr; free: - destroy_hist_field(operand1, 0); - destroy_hist_field(operand2, 0); + if (!expr || expr->operand[0] != operand1) + destroy_hist_field(operand1, 0); + if (!expr || expr->operand[1] != operand2) + destroy_hist_field(operand2, 0); destroy_hist_field(expr, 0); return ERR_PTR(ret); I'm worried about the complexity of having to know where to free what, and not just figuring it out at the end. -- Steve