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 19:51:43 +0300 Message-ID: <4c183bd4-bb51-4c4e-d097-998b213bef66@gmail.com> References: <20210906041330.2065214-1-mudongliangabcd@gmail.com> <53fb4217-21b8-ac46-bb39-581a4c9837a4@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=HDKqg2pWAZz4uZmdk0aehi0Cj5oQsrM+ze2oyg6/ka8=; b=IYR+4FWNbNbEfelaudwpyUei6jY6Xb0GzO8X/1E/jU338wA8vM5Ic6okiyjA6h6UjS /sf2UZAhLKmHMyDVEftgpJfeb2LkIqyMS22JBeoKm1ZzmS9uoSh776B7rmQu45Tr1Eyk b6g1ie+tI5xu0EtLAO3cMhHUbB5iNznRN/uPtsvYuv9wYBTQ/Kdlt27slMyS5nEh/DbN EiV6fiejJ3Acp1z/Dmh0Jw3K6ZT3DeJiYlYg96k03C5ixCeRPeuD6ZVS9jglq5amgIsy U/DsYGO9mgVQLRRajEwjmCSNnR+p4kzcs26Nb4+zflSzZAaedSblsjvkvIC642Rj6tra meuA== Content-Language: en-US In-Reply-To: <53fb4217-21b8-ac46-bb39-581a4c9837a4-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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 19:47, Pavel Skripkin wrote: > 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 :) > > Also, I think, we should add kobject_put() call to 1. nilfs_sysfs_create_##name##_group 2. nilfs_sysfs_create_snapshot_group To prevent other random kobject memory leaks in nilfs... With regards, Pavel Skripkin