Messages in this thread | | | From | Dongliang Mu <> | Date | Fri, 21 Jan 2022 11:47:26 +0800 | Subject | Re: Fw:Re: [PATCH] fs: nilfs2: fix memory leak in nilfs sysfs create device group |
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> > From: Ryusuke Konishi <konishi.ryusuke@gmail.com> > Date: 01/21/2022 01:54 > To: Dongliang Mu <dzm91@hust.edu.cn> > Cc: Pavel Skripkin <paskripkin@gmail.com> 、 Andrew Morton <akpm@linux-foundation.org> 、 linux-nilfs <linux-nilfs@vger.kernel.org> 、 LKML <linux-kernel@vger.kernel.org> 、 Nanyong Sun <sunnanyong@huawei.com> > Subject: Re: [PATCH] fs: nilfs2: fix memory leak in nilfs_sysfs_create_device_group > (added Nanyong Sun to CC) > Hi Dongliang, > > On Thu, Jan 20, 2022 at 11:07 PM Pavel Skripkin <paskripkin@gmail.com> wrote: > > > Hi Dongliang, > > On 1/20/22 16:44, Dongliang Mu wrote: > > The preivous commit 8fd0c1b0647a ("nilfs2: fix memory leak in > nilfs_sysfs_delete_device_group") only handles the memory leak in the > nilfs_sysfs_delete_device_group. However, the similar memory leak still > occurs in the nilfs_sysfs_create_device_group. > > Fix it by adding kobject_del when > kobject_init_and_add succeeds, but one of the following calls fails. > > Fixes: 8fd0c1b0647a ("nilfs2: fix memory leak in nilfs_sysfs_delete_device_group") > > > Why Fixes tag points to my commit? This issue was introduced before my patch > > > As Pavel pointed out, this patch is independent of his patch. > The following one ?
Hi Pavel,
This is an incorrect fixes tag. I need to dig more about `git log -p fs/nilfs2/sysfs.c`.
I wonder if there are any automatic or semi-automatic ways to capture this fixes tag. Or how do you guys identify the fixes tag?
> > 5f5dec07aca7 ("nilfs2: fix memory leak in nilfs_sysfs_create_device_group") > > Signed-off-by: Dongliang Mu <dzm91@hust.edu.cn> > --- > fs/nilfs2/sysfs.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > > Can you describe what memory leak issue does this patch actually fix ? > > It looks like kobject_put() can call __kobject_del() unless circular > references exist. > > kobject_put() -> kref_put() -> kobject_release() -> > kobject_cleanup() -> __kobject_del() > > As explained in Documentation/core-api/kobject.rst, > > kobject_del() can be used to drop the reference to the parent object, if > circular references are constructed. > > But, at least, the parent object is NULL in this case. > I really want to understand what the real problem is. > > Thanks, > Ryusuke Konishi
I know where my problem is. From the disconnect function, I think the kobject_del and kobject_put are both necessary without checking the documentation of kobjects.
Then I think the current error handling may miss kobject_del, and this patch is generated.
As a result, I think we can ignore this patch. Sorry for my false alarm.
> > > diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c > index 379d22e28ed6..0b2db2b499d5 100644 > --- a/fs/nilfs2/sysfs.c > +++ b/fs/nilfs2/sysfs.c > @@ -995,7 +995,7 @@ int nilfs_sysfs_create_device_group(struct super_block *sb) > > err = nilfs_sysfs_create_mounted_snapshots_group(nilfs); > if (err) > - goto cleanup_dev_kobject; > + goto delete_dev_kobject; > > err = nilfs_sysfs_create_checkpoints_group(nilfs); > if (err) > @@ -1027,6 +1027,9 @@ int nilfs_sysfs_create_device_group(struct super_block *sb) > delete_mounted_snapshots_group: > nilfs_sysfs_delete_mounted_snapshots_group(nilfs); > > +delete_dev_kobject: > + kobject_del(&nilfs->ns_dev_kobj); > + > cleanup_dev_kobject: > kobject_put(&nilfs->ns_dev_kobj); > kfree(nilfs->ns_dev_subgroups); > > With regards, > Pavel Skripkin
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