linux-kernel - RE: [BUG]is there a refcount leak in function mei_me_cl_rm_by

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Date:   Thu, 7 May 2020 18:50:50 +0000
From:   "Winkler, Tomas" <tomas.winkler@...el.com>
To:     亿一 <teroincn@...il.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [BUG]is there a refcount leak in function mei_me_cl_rm_by_uuid?



> -----Original Message-----
> From: 亿一 <teroincn@...il.com>
> Sent: Wednesday, May 06, 2020 17:47
> To: Winkler, Tomas <tomas.winkler@...el.com>
> Cc: linux-kernel@...r.kernel.org
> Subject: [BUG]is there a refcount leak in function mei_me_cl_rm_by_uuid?

Unfortunately you are correct,  but currently it is very hard to hit the issue in real life.
The patch is coming. 
Thanks
Tomas


> 
> HI, all
> When reviewing function mei_me_cl_rm_by_uuid， I notice that function
> __mei_me_cl_by_uuid increases me_cl refcount and function _mei_me_cl_del
> delete a list node with decrement me_cl refcount , actually here cause a
> refcount leak as we haven't release the refcount by __mei_me_cl_by_uuid  ?
> similar issue happens in mei_me_cl_rm_by_uuid_id too.
> 
> void mei_me_cl_rm_by_uuid(struct mei_device *dev, const uuid_le *uuid) {
>     struct mei_me_client *me_cl;
> 
>     dev_dbg(dev->dev, "remove %pUl\n", uuid);
> 
>     down_write(&dev->me_clients_rwsem);
>     me_cl = __mei_me_cl_by_uuid(dev, uuid); /* increase a refcount */
>     __mei_me_cl_del(dev, me_cl); /* release the refcount with a list node deteled
> */
>     up_write(&dev->me_clients_rwsem);
> }
> 
> Best regards,
> 
> Lin Yi.