Subject: Re: [PATCH] optee: Suppress false positive kmemleak report in
 optee_handle_rpc()
To:     Sumit Garg <sumit.garg@linaro.org>
Cc:     Jerome Forissier <jerome@forissier.org>,
        "op-tee@lists.trustedfirmware.org" <op-tee@lists.trustedfirmware.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jens Wiklander <jens.wiklander@linaro.org>,
        Etienne Carriere <etienne.carriere@linaro.org>
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From:   wangxiaolei <xiaolei.wang@windriver.com>
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On 12/13/21 5:04 PM, Sumit Garg wrote:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
> On Mon, 13 Dec 2021 at 14:25, wangxiaolei <xiaolei.wang@windriver.com> wrote:
>>
>> On 12/10/21 5:38 PM, Sumit Garg wrote:
>>> [Please note: This e-mail is from an EXTERNAL e-mail address]
>>>
>>> On Fri, 10 Dec 2021 at 13:40, Jerome Forissier <jerome@forissier.org> wrote:
>>>> +CC Jens, Etienne
>>>>
>>>> On 12/10/21 06:00, Sumit Garg wrote:
>>>>> On Fri, 10 Dec 2021 at 09:42, Wang, Xiaolei <Xiaolei.Wang@windriver.com> wrote:
>>>>>> -----Original Message-----
>>>>>> From: Sumit Garg <sumit.garg@linaro.org>
>>>>>> Sent: Thursday, December 9, 2021 7:41 PM
>>>>>> To: Wang, Xiaolei <Xiaolei.Wang@windriver.com>
>>>>>> Cc: jens.wiklander@linaro.org; op-tee@lists.trustedfirmware.org; linux-kernel@vger.kernel.org
>>>>>> Subject: Re: [PATCH] optee: Suppress false positive kmemleak report in optee_handle_rpc()
>>>>>>
>>>>>> [Please note: This e-mail is from an EXTERNAL e-mail address]
>>>>>>
>>>>>> On Mon, 6 Dec 2021 at 17:35, Xiaolei Wang <xiaolei.wang@windriver.com> wrote:
>>>>>>> We observed the following kmemleak report:
>>>>>>> unreferenced object 0xffff000007904500 (size 128):
>>>>>>>     comm "swapper/0", pid 1, jiffies 4294892671 (age 44.036s)
>>>>>>>     hex dump (first 32 bytes):
>>>>>>>       00 47 90 07 00 00 ff ff 60 00 c0 ff 00 00 00 00  .G......`.......
>>>>>>>       60 00 80 13 00 80 ff ff a0 00 00 00 00 00 00 00  `...............
>>>>>>>     backtrace:
>>>>>>>       [<000000004c12b1c7>] kmem_cache_alloc+0x1ac/0x2f4
>>>>>>>       [<000000005d23eb4f>] tee_shm_alloc+0x78/0x230
>>>>>>>       [<00000000794dd22c>] optee_handle_rpc+0x60/0x6f0
>>>>>>>       [<00000000d9f7c52d>] optee_do_call_with_arg+0x17c/0x1dc
>>>>>>>       [<00000000c35884da>] optee_open_session+0x128/0x1ec
>>>>>>>       [<000000001748f2ff>] tee_client_open_session+0x28/0x40
>>>>>>>       [<00000000aecb5389>] optee_enumerate_devices+0x84/0x2a0
>>>>>>>       [<000000003df18bf1>] optee_probe+0x674/0x6cc
>>>>>>>       [<000000003a4a534a>] platform_drv_probe+0x54/0xb0
>>>>>>>       [<000000000c51ce7d>] really_probe+0xe4/0x4d0
>>>>>>>       [<000000002f04c865>] driver_probe_device+0x58/0xc0
>>>>>>>       [<00000000b485397d>] device_driver_attach+0xc0/0xd0
>>>>>>>       [<00000000c835f0df>] __driver_attach+0x84/0x124
>>>>>>>       [<000000008e5a429c>] bus_for_each_dev+0x70/0xc0
>>>>>>>       [<000000001735e8a8>] driver_attach+0x24/0x30
>>>>>>>       [<000000006d94b04f>] bus_add_driver+0x104/0x1ec
>>>>>>>
>>>>>>> This is not a memory leak because we pass the share memory pointer to
>>>>>>> secure world and would get it from secure world before releasing it.
>>>>>>> How about if it's actually a memory leak caused by the secure world?
>>>>>>> An example being secure world just allocates kernel memory via OPTEE_SMC_RPC_FUNC_ALLOC and doesn't free it via OPTEE_SMC_RPC_FUNC_FREE.
>>>>>>> IMO, we need to cross-check optee-os if it's responsible for leaking kernel memory.
>>>>>> Hi sumit,
>>>>>>
>>>>>> You mean we need to check whether there is a real memleak,
>>>>>> If being secure world just allocate kernel memory via OPTEE_SMC_PRC_FUNC_ALLOC and until the end, there is no free
>>>>>> It via OPTEE_SMC_PRC_FUNC_FREE, then we should judge it as a memory leak, wo need to judge whether it is caused by secure os?
>>>>> Yes. AFAICT, optee-os should allocate shared memory to communicate
>>>>> with tee-supplicant. So once the communication is done, the underlying
>>>>> shared memory should be freed. I can't think of any scenario where
>>>>> optee-os should keep hold-off shared memory indefinitely.
>>>> I believe it can happen when OP-TEE's CFG_PREALLOC_RPC_CACHE is y. See
>>>> the config file [1] and the commit which introduced this config [2].
>>> Okay, I see the reasoning. So during the OP-TEE driver's lifetime, the
>>> RPC shared memory remains allocated. I guess that is done primarily
>>> for performance reasons.
>>>
>>> But still it doesn't feel appropriate that we term all RPC shm
>>> allocations as not leaking memory as we might miss obvious ones.
>>>
>>> Xiaolei,
>>>
>>> Can you once test with CFG_PREALLOC_RPC_CACHE=n while compiling
>>> optee-os and see if the observed memory leak disappears or not?
>>>
>>> -Sumit
>> Hi sumit
>>
>>
>> The version I am using has not increased the CFG_PREALLOC_RPC_CACHE
>>
>> switch, I checked out to the latest version, but because of the need for
>>
>> additional patches for the imx8 platform, I still have no way to test the
>>
>> CFG_PREALLOC_RPC_CACHE=n situation
>>
> Can you just try to backport this [1] patch to your imx8 optee-os tree and test?
>
> [1] https://github.com/OP-TEE/optee_os/commit/8887663248ad

Hi sumit

I upgraded optee-os from version 3.2.0 to 3.13.0, and the kernel did not 
detect this problem.

I have not set CFG_PREALLOC_RPC_CACHE to n. This should be a problem 
that occurs when compatible

with lower versions.


thanks

xiaolei

>
> -Sumit
>
>> thanks
>>
>> xiaolei
>>
>>>> [1] https://github.com/OP-TEE/optee_os/blob/3.15.0/mk/config.mk#L709
>>>> [2] https://github.com/OP-TEE/optee_os/commit/8887663248ad
>>>>
>>>> --
>>>> Jerome