Messages in this thread | | | Date | Thu, 20 Oct 2022 10:06:48 +0800 | Subject | Re: [PATCH] ocfs2: possible memory leak in mlog_sys_init() | From | Joseph Qi <> |
| |
On 10/19/22 10:57 AM, Yang Yingliang wrote: > > On 2022/10/19 10:26, Joseph Qi wrote: >> >> On 10/18/22 10:28 PM, Yang Yingliang wrote: >>> On 2022/10/18 21:39, Joseph Qi wrote: >>>> On 10/18/22 6:33 PM, Yang Yingliang wrote: >>>>> 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. >>>>> Yes, you are right. I've mixed the two ksets up. >>>> In theory, kset_register() may return error because of a NULL kset, so >>>> here we may not call kset_put() directly, I'm not sure if a static >>>> checker will happy. >>>> Though this can't happen since it's already statically allocated... >>> kset_register() may fail if kobject_add_internal() return error (can't allocate memory), the name >>> "logmask" is dynamically alloctated while ocfs2 is compile as module and insert it (if ocfs2 is >>> built in kernel, the name is constant, it won't cause a leak), so the name can be leaked. >> What I mean is kset_register() may fail with many reasons, or even >> without kset_init(). >> I wonder if we have to handle this internal kset_register(), but not >> leave it to caller. This may benefit other callers as well. >> >> Something like: >> err = kobject_add_internal(&k->kobj); >> if (err) { >> kset_put(k); >> return err; >> } > I had think about this method to fix this, but some kset is allocated dynamically in driver and > it's freed in callback function which is called after kset_put() and in error path in driver will free > it again, it leads double free in some drivers. > I don't think it's good idea that caller has to take care part of the internal logic of kset_register() in case of error. Hi Greg, what do you think?
Thanks, Joseph
> I think kset_register() is similar with device_register(), if it fails need another put function to give > up reference in driver. >
| |