From nobody Sat Apr 18 21:04:03 2026 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 A6E30C43334 for ; Mon, 11 Jul 2022 01:50:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229653AbiGKBuS (ORCPT ); Sun, 10 Jul 2022 21:50:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47542 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229614AbiGKBuJ (ORCPT ); Sun, 10 Jul 2022 21:50:09 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 933CB18371; Sun, 10 Jul 2022 18:50:00 -0700 (PDT) Received: from dggpeml500022.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Lh6GD5bkyzkWbV; Mon, 11 Jul 2022 09:47:48 +0800 (CST) Received: from dggpeml100012.china.huawei.com (7.185.36.121) by dggpeml500022.china.huawei.com (7.185.36.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 11 Jul 2022 09:49:57 +0800 Received: from ubuntu1804.huawei.com (10.67.174.66) by dggpeml100012.china.huawei.com (7.185.36.121) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 11 Jul 2022 09:49:57 +0800 From: Zheng Yejian To: CC: , , , , , , Subject: [PATCH v2] tracing/histograms: Fix memory leak problem Date: Mon, 11 Jul 2022 09:47:31 +0800 Message-ID: <20220711014731.69520-1-zhengyejian1@huawei.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220708210335.79a38356@gandalf.local.home> References: <20220708210335.79a38356@gandalf.local.home> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [10.67.174.66] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml100012.china.huawei.com (7.185.36.121) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This reverts commit 46bbe5c671e06f070428b9be142cc4ee5cedebac. As commit 46bbe5c671e0 ("tracing: fix double free") said, the "double free" problem reported by clang static analyzer is: > In parse_var_defs() if there is a problem allocating > var_defs.expr, the earlier var_defs.name is freed. > This free is duplicated by free_var_defs() which frees > the rest of the list. However, if there is a problem allocating N-th var_defs.expr: + in parse_var_defs(), the freed 'earlier var_defs.name' is actually the N-th var_defs.name; + then in free_var_defs(), the names from 0th to (N-1)-th are freed; IF ALLOCATING PROBLEM HAPPENED HERE!!! -+ \ | 0th 1th (N-1)-th N-th V +-------------+-------------+-----+-------------+----------- var_defs: | name | expr | name | expr | ... | name | expr | name | /// +-------------+-------------+-----+-------------+----------- These two frees don't act on same name, so there was no "double free" problem before. Conversely, after that commit, we get a "memory leak" problem because the above "N-th var_defs.name" is not freed. If enable CONFIG_DEBUG_KMEMLEAK and inject a fault at where the N-th var_defs.expr allocated, then execute on shell like: $ echo 'hist:key=3Dcall_site:val=3D$v1,$v2:v1=3Dbytes_req,v2=3Dbytes_allo= c' > \ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger Then kmemleak reports: unreferenced object 0xffff8fb100ef3518 (size 8): comm "bash", pid 196, jiffies 4295681690 (age 28.538s) hex dump (first 8 bytes): 76 31 00 00 b1 8f ff ff v1...... backtrace: [<0000000038fe4895>] kstrdup+0x2d/0x60 [<00000000c99c049a>] event_hist_trigger_parse+0x206f/0x20e0 [<00000000ae70d2cc>] trigger_process_regex+0xc0/0x110 [<0000000066737a4c>] event_trigger_write+0x75/0xd0 [<000000007341e40c>] vfs_write+0xbb/0x2a0 [<0000000087fde4c2>] ksys_write+0x59/0xd0 [<00000000581e9cdf>] do_syscall_64+0x3a/0x80 [<00000000cf3b065c>] entry_SYSCALL_64_after_hwframe+0x46/0xb0 Cc: stable@vger.kernel.org Fixes: 46bbe5c671e0 ("tracing: fix double free") Reported-by: Hulk Robot Suggested-by: Steven Rostedt Signed-off-by: Zheng Yejian Reviewed-by: Tom Zanussi --- kernel/trace/trace_events_hist.c | 2 ++ 1 file changed, 2 insertions(+) Changes since v1: - Assign 'NULL' after 'kfree' for safety as suggested by Steven - Rename commit title and add Suggested-by tag diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_h= ist.c index 48e82e141d54..e87a46794079 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -4430,6 +4430,8 @@ static int parse_var_defs(struct hist_trigger_data *h= ist_data) =20 s =3D kstrdup(field_str, GFP_KERNEL); if (!s) { + kfree(hist_data->attrs->var_defs.name[n_vars]); + hist_data->attrs->var_defs.name[n_vars] =3D NULL; ret =3D -ENOMEM; goto free; } --=20 2.32.0