From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Skripkin Subject: Re: [PATCH] nilfs2: fix memory leak in nilfs_sysfs_create_device_group Date: Mon, 6 Sep 2021 19:47:33 +0300 Message-ID: <53fb4217-21b8-ac46-bb39-581a4c9837a4@gmail.com> References: <20210906041330.2065214-1-mudongliangabcd@gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language :from:to:cc:references:in-reply-to:content-transfer-encoding; bh=hj6jr/Bay+4stbYvb9h9fv4qa8ImPa2qelZrSXh4XGM=; b=NaeQ3lsb689M28sB2sF8AhjeWPoYlRdGxderE/wKH+GaDVw+FKFIp/0J/H+Z2HHTgN acNmsPgmOdUWAq/2GojBGc7dGIzudvLPvd1htq2EqpTXzhyPQXomquidRBJsufcjn2dc qweTVD10sEgFfK/uv/7JHh4EEO04M4sd9ZsRoHrolMxc4meFecIFDqMQ/+/L6DBijDQq mXXBz+vUG3YllgBqoXAmv5NaisL/OnGiS/3e9gp28ZvUxj74xmYuV2N0rvlNrRPEU1pj rFJj9pQoYQYynT6kLilZ3X1kLTokqjpGXtk85lGX2Ax8I/LbiqPk3Y7uFpHoLS/ZdP+s anXg== Content-Language: en-US In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Dongliang Mu , Ryusuke Konishi Cc: linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel On 9/6/21 18:56, Pavel Skripkin wrote: > On 9/6/21 08:43, Dongliang Mu wrote: >> On Mon, Sep 6, 2021 at 12:13 PM Dongliang Mu wrote: >>> >>> The commit 8fd0c1b0647a ("nilfs2: fix memory leak in >>> nilfs_sysfs_delete_device_group") adds a kobject_put to free the leaking >>> object name. However, it is incomplete to only add kobject_put in the >>> nilfs_sysfs_delete_device_group. The function >>> nilfs_sysfs_create_device_group also needs the kobject_put to >>> free the object name in the error handling part. >>> >>> Fix this by adding kobject_put in the error handling code of >>> nilfs_sysfs_create_device_group. >> >> Even after I add this patch, my local syzkaller still reports this >> memory leak one hour later. Therefore, there are some other paths or >> magics which can trigger the memory leak. I need to dig deeper. >> >> Pavel, do you have any idea about this crash report? >> >> BUG: memory leak >> unreferenced object 0xffff88804a1a8a60 (size 32): >> comm "syz-executor", pid 14551, jiffies 4294960586 (age 14.780s) >> hex dump (first 32 bytes): >> 6c 6f 6f 70 35 00 00 00 00 00 00 00 00 00 00 00 loop5........... >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace: >> [] kstrdup+0x36/0x70 >> [] kstrdup_const+0x53/0x80 >> [] kvasprintf_const+0xc2/0x110 >> [] kobject_set_name_vargs+0x3b/0xe0 >> [] kobject_init_and_add+0x6d/0xc0 >> [] nilfs_sysfs_create_device_group+0x98/0x3a0 >> [] init_nilfs+0x424/0x580 >> [] nilfs_mount+0x532/0x8c0 >> [] legacy_get_tree+0x2b/0x90 >> [] vfs_get_tree+0x28/0x100 >> [] path_mount+0xb92/0xfe0 >> [] do_mount+0xa1/0xc0 >> [] __x64_sys_mount+0xf4/0x160 >> [] do_syscall_64+0x35/0xb0 >> [] entry_SYSCALL_64_after_hwframe+0x44/0xae >> >> > > Hi, Dongliang! > > > This report says nothing to me... It shows, that there is missing > kobject_put() somewhere. I think, we need a reproducer for this leak, > otherwise only code review can help :( > > > Hm, I guess, I see... We should call kobject_put() in case of kobject_init_and_add() failure: lib/kobject.c:459 * If this function returns an error, kobject_put() must be called to * properly clean up the memory associated with the object. This is the so I suggest: diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c index 68e8d61e28dd..e8717f4ba2a1 100644 --- a/fs/nilfs2/sysfs.c +++ b/fs/nilfs2/sysfs.c @@ -1026,6 +1026,7 @@ int nilfs_sysfs_create_device_group(struct super_block *sb) kobject_del(&nilfs->ns_dev_kobj); free_dev_subgroups: + kobject_put(&nilfs->ns_dev_kobj); kfree(nilfs->ns_dev_subgroups); failed_create_device_group: This patch should fix 2 memory leaks :) With regards, Pavel Skripkin