Re: [PATCH] ocfs2: possible memory leak in mlog_sys_init()

[Joseph Qi <joseph.qi@linux.alibaba.com>]

Hi,

On 10/18/22 3:52 PM, Yang Yingliang wrote:
> Inject fault while probing module, kset_register() may fail,
> if it fails, but the refcount of kobject is not decreased to
> 0, the name allocated in kobject_set_name() is leaked. Fix
> this by calling kset_put(), so that name can be freed in
> callback function kobject_cleanup().
> 
> unreferenced object 0xffff888100da9348 (size 8):
>   comm "modprobe", pid 257, jiffies 4294701096 (age 33.334s)
>   hex dump (first 8 bytes):
>     6c 6f 67 6d 61 73 6b 00                          logmask.
>   backtrace:
>     [<00000000306e441c>] __kmalloc_node_track_caller+0x44/0x1b0
>     [<000000007c491a9e>] kstrdup+0x3a/0x70
>     [<0000000015719a3b>] kstrdup_const+0x63/0x80
>     [<0000000084e458ea>] kvasprintf_const+0x149/0x180
>     [<0000000091302b42>] kobject_set_name_vargs+0x56/0x150
>     [<000000005f48eeac>] kobject_set_name+0xab/0xe0
> 
> Fixes: 34980ca8faeb ("Drivers: clean up direct setting of the name of a kset")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>  fs/ocfs2/cluster/masklog.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ocfs2/cluster/masklog.c b/fs/ocfs2/cluster/masklog.c
> index 563881ddbf00..7f9ba816d955 100644
> --- a/fs/ocfs2/cluster/masklog.c
> +++ b/fs/ocfs2/cluster/masklog.c
> @@ -156,6 +156,7 @@ static struct kset mlog_kset = {
>  int mlog_sys_init(struct kset *o2cb_kset)
>  {
>  	int i = 0;
> +	int ret;
>  
>  	while (mlog_attrs[i].attr.mode) {
>  		mlog_default_attrs[i] = &mlog_attrs[i].attr;
> @@ -165,7 +166,11 @@ int mlog_sys_init(struct kset *o2cb_kset)
>  
>  	kobject_set_name(&mlog_kset.kobj, "logmask");
>  	mlog_kset.kobj.kset = o2cb_kset;
> -	return kset_register(&mlog_kset);
> +	ret = kset_register(&mlog_kset);

If register fails, it will call unregister in o2cb_sys_init(), which
will put kobject.

Thanks,
Joseph

> +	if (ret)
> +		kset_put(&mlog_kset);
> +
> +	return ret;
>  }
>  
>  void mlog_sys_shutdown(void)