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 8A532C433F5 for ; Mon, 6 Dec 2021 13:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244371AbhLFN2D (ORCPT ); Mon, 6 Dec 2021 08:28:03 -0500 Received: from szxga01-in.huawei.com ([45.249.212.187]:32880 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241389AbhLFN2B (ORCPT ); Mon, 6 Dec 2021 08:28:01 -0500 Received: from dggpeml500020.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4J74045l9hzcbmZ; Mon, 6 Dec 2021 21:24:20 +0800 (CST) Received: from huawei.com (10.175.127.227) by dggpeml500020.china.huawei.com (7.185.36.88) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Mon, 6 Dec 2021 21:24:31 +0800 From: Baokun Li To: , , , , CC: , , , , , Hulk Robot Subject: [PATCH -next] kfence: fix memory leak when cat kfence objects Date: Mon, 6 Dec 2021 21:36:28 +0800 Message-ID: <20211206133628.2822545-1-libaokun1@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpeml500020.china.huawei.com (7.185.36.88) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hulk robot reported a kmemleak problem: ----------------------------------------------------------------------- unreferenced object 0xffff93d1d8cc02e8 (size 248): comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s) hex dump (first 32 bytes): 00 40 85 19 d4 93 ff ff 00 10 00 00 00 00 00 00 .@.............. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000db5610b3>] seq_open+0x2a/0x80 [<00000000d66ac99d>] full_proxy_open+0x167/0x1e0 [<00000000d58ef917>] do_dentry_open+0x1e1/0x3a0 [<0000000016c91867>] path_openat+0x961/0xa20 [<00000000909c9564>] do_filp_open+0xae/0x120 [<0000000059c761e6>] do_sys_openat2+0x216/0x2f0 [<00000000b7a7b239>] do_sys_open+0x57/0x80 [<00000000e559d671>] do_syscall_64+0x33/0x40 [<000000000ea1fbfd>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 unreferenced object 0xffff93d419854000 (size 4096): comm "cat", pid 23327, jiffies 4624670141 (age 495992.217s) hex dump (first 32 bytes): 6b 66 65 6e 63 65 2d 23 32 35 30 3a 20 30 78 30 kfence-#250: 0x0 30 30 30 30 30 30 30 37 35 34 62 64 61 31 32 2d 0000000754bda12- backtrace: [<000000008162c6f2>] seq_read_iter+0x313/0x440 [<0000000020b1b3e3>] seq_read+0x14b/0x1a0 [<00000000af248fbc>] full_proxy_read+0x56/0x80 [<00000000f97679d1>] vfs_read+0xa5/0x1b0 [<000000000ed8a36f>] ksys_read+0xa0/0xf0 [<00000000e559d671>] do_syscall_64+0x33/0x40 [<000000000ea1fbfd>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 ----------------------------------------------------------------------- I find that we can easily reproduce this problem with the following commands: `cat /sys/kernel/debug/kfence/objects` `echo scan > /sys/kernel/debug/kmemleak` `cat /sys/kernel/debug/kmemleak` The leaked memory is allocated in the stack below: ---------------------------------- do_syscall_64 do_sys_open do_dentry_open full_proxy_open seq_open ---> alloc seq_file vfs_read full_proxy_read seq_read seq_read_iter traverse ---> alloc seq_buf ---------------------------------- And it should have been released in the following process: ---------------------------------- do_syscall_64 syscall_exit_to_user_mode exit_to_user_mode_prepare task_work_run ____fput __fput full_proxy_release ---> free here ---------------------------------- However, the release function corresponding to file_operations is not implemented in kfence. As a result, a memory leak occurs. Therefore, the solution to this problem is to implement the corresponding release function. Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Reported-by: Hulk Robot Signed-off-by: Baokun Li --- mm/kfence/core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 46103a7628a6..186838f062b2 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -684,6 +684,7 @@ static const struct file_operations objects_fops = { .open = open_objects, .read = seq_read, .llseek = seq_lseek, + .release = seq_release, }; static int __init kfence_debugfs_init(void) -- 2.31.1