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 4388FC41513 for ; Wed, 16 Aug 2023 01:46:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235169AbjHPBpi (ORCPT ); Tue, 15 Aug 2023 21:45:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234800AbjHPBpL (ORCPT ); Tue, 15 Aug 2023 21:45:11 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 51E0F10D1; Tue, 15 Aug 2023 18:45:07 -0700 (PDT) Received: from dggpeml500012.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4RQW7x2R34zNmrj; Wed, 16 Aug 2023 09:41:33 +0800 (CST) Received: from [10.67.110.218] (10.67.110.218) by dggpeml500012.china.huawei.com (7.185.36.15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Wed, 16 Aug 2023 09:45:04 +0800 Message-ID: <32583a11-9cbd-9b4d-34be-551babed6f51@huawei.com> Date: Wed, 16 Aug 2023 09:45:04 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH] tracing: Fix memleak due to race between current_tracer and trace Content-Language: en-US To: , CC: , , , References: <20230808092905.2936459-1-zhengyejian1@huawei.com> From: Zheng Yejian In-Reply-To: <20230808092905.2936459-1-zhengyejian1@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.110.218] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500012.china.huawei.com (7.185.36.15) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org On 2023/8/8 17:29, Zheng Yejian wrote: > Kmemleak report a leak in graph_trace_open(): > > unreferenced object 0xffff0040b95f4a00 (size 128): > comm "cat", pid 204981, jiffies 4301155872 (age 99771.964s) > hex dump (first 32 bytes): > e0 05 e7 b4 ab 7d 00 00 0b 00 01 00 00 00 00 00 .....}.......... > f4 00 01 10 00 a0 ff ff 00 00 00 00 65 00 10 00 ............e... > backtrace: > [<000000005db27c8b>] kmem_cache_alloc_trace+0x348/0x5f0 > [<000000007df90faa>] graph_trace_open+0xb0/0x344 > [<00000000737524cd>] __tracing_open+0x450/0xb10 > [<0000000098043327>] tracing_open+0x1a0/0x2a0 > [<00000000291c3876>] do_dentry_open+0x3c0/0xdc0 > [<000000004015bcd6>] vfs_open+0x98/0xd0 > [<000000002b5f60c9>] do_open+0x520/0x8d0 > [<00000000376c7820>] path_openat+0x1c0/0x3e0 > [<00000000336a54b5>] do_filp_open+0x14c/0x324 > [<000000002802df13>] do_sys_openat2+0x2c4/0x530 > [<0000000094eea458>] __arm64_sys_openat+0x130/0x1c4 > [<00000000a71d7881>] el0_svc_common.constprop.0+0xfc/0x394 > [<00000000313647bf>] do_el0_svc+0xac/0xec > [<000000002ef1c651>] el0_svc+0x20/0x30 > [<000000002fd4692a>] el0_sync_handler+0xb0/0xb4 > [<000000000c309c35>] el0_sync+0x160/0x180 > > The root cause is descripted as follows: > > __tracing_open() { // 1. File 'trace' is being opened; > ... > *iter->trace = *tr->current_trace; // 2. Tracer 'function_graph' is > // currently set; > ... > iter->trace->open(iter); // 3. Call graph_trace_open() here, > // and memory are allocated in it; > ... > } > > s_start() { // 4. The opened file is being read; > ... > *iter->trace = *tr->current_trace; // 5. If tracer is switched to > // 'nop' or others, then memory > // in step 3 are leaked!!! > ... > } > > To fix it, in s_start(), close tracer before switching then reopen the > new tracer after switching. > > Fixes: d7350c3f4569 ("tracing/core: make the read callbacks reentrants") > Signed-off-by: Zheng Yejian > --- > kernel/trace/trace.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > index b8870078ef58..d50a0227baa3 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -4213,8 +4213,15 @@ static void *s_start(struct seq_file *m, loff_t *pos) > * will point to the same string as current_trace->name. > */ > mutex_lock(&trace_types_lock); > - if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) > + if (unlikely(tr->current_trace && iter->trace->name != tr->current_trace->name)) { > + /* Close iter->trace before switching to the new current tracer */ > + if (iter->trace->close) > + iter->trace->close(iter); Hi, kasan report an issue related to this patch in v5.10, I'll handle it and then send V2 if the patch needs to be changed. BUG: KASAN: use-after-free in graph_trace_close+0x78/0x7c Read of size 8 at addr ffff204054ca8f00 by task cat/193541 [...] Call trace: dump_backtrace+0x0/0x3e4 show_stack+0x20/0x2c dump_stack+0x140/0x198 print_address_description.constprop.0+0x2c/0x1fc __kasan_report+0xe0/0x140 kasan_report+0x44/0x5c __asan_report_load8_noabort+0x34/0x60 graph_trace_close+0x78/0x7c wakeup_trace_close+0x3c/0x54 s_start+0x4f4/0x794 seq_read_iter+0x210/0xd90 seq_read+0x288/0x410 vfs_read+0x13c/0x41c ksys_read+0xf4/0x1e0 __arm64_sys_read+0x74/0xa4 el0_svc_common.constprop.0+0xfc/0x394 do_el0_svc+0xac/0xec el0_svc+0x20/0x30 el0_sync_handler+0xb0/0xb4 el0_sync+0x160/0x180 Allocated by task 193541: kasan_save_stack+0x28/0x60 __kasan_kmalloc.constprop.0+0xa4/0xd0 kasan_kmalloc+0x10/0x20 kmem_cache_alloc_trace+0x2ec/0x5f0 graph_trace_open+0xb0/0x344 __tracing_open+0x450/0xb10 tracing_open+0x1a0/0x2a0 do_dentry_open+0x3c0/0xdc0 vfs_open+0x98/0xd0 do_open+0x520/0x8d0 > *iter->trace = *tr->current_trace; > + /* Reopen the new current tracer */ > + if (iter->trace->open) > + iter->trace->open(iter); > + } > mutex_unlock(&trace_types_lock); > > #ifdef CONFIG_TRACER_MAX_TRACE