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SubjectRe: [PATCH] ocfs2: possible memory leak in mlog_sys_init()
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Hi,

On 2022/10/18 17:02, Joseph Qi wrote:
> 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.
They are different ksets, the kset unregistered in o2cb_sys_init() is
'o2cb_kset', the
kset used to registered in mlog_sys_init() is 'mlog_kset', and they hold
difference
refcounts.

Thanks,
Yang
>
> Thanks,
> Joseph
>
>> + if (ret)
>> + kset_put(&mlog_kset);
>> +
>> + return ret;
>> }
>>
>> void mlog_sys_shutdown(void)
> .

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