linux-kernel - Re: [PATCH] optee: Suppress false positive kmemleak report in optee_handle

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Message-ID: <CAFA6WYNh6WmkeZFCOPJpu69ypyWc7itMBdhTg3yqnH0MbOhFcQ@mail.gmail.com>
Date:   Tue, 14 Dec 2021 12:59:29 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     wangxiaolei <xiaolei.wang@...driver.com>
Cc:     Jerome Forissier <jerome@...issier.org>,
        "op-tee@...ts.trustedfirmware.org" <op-tee@...ts.trustedfirmware.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Etienne Carriere <etienne.carriere@...aro.org>
Subject: Re: [PATCH] optee: Suppress false positive kmemleak report in optee_handle_rpc()

On Tue, 14 Dec 2021 at 12:41, wangxiaolei <xiaolei.wang@...driver.com> wrote:
>
>
> 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@...driver.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@...issier.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@...driver.com> wrote:
> >>>>>> -----Original Message-----
> >>>>>> From: Sumit Garg <sumit.garg@...aro.org>
> >>>>>> Sent: Thursday, December 9, 2021 7:41 PM
> >>>>>> To: Wang, Xiaolei <Xiaolei.Wang@...driver.com>
> >>>>>> Cc: jens.wiklander@...aro.org; op-tee@...ts.trustedfirmware.org; linux-kernel@...r.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@...driver.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.

Can you check if CFG_TEE_CORE_EMBED_INTERNAL_TESTS is enabled in
optee-os version 3.13.0? As we would require atleast one RPC prealloc
SHM invocation from OP-TEE for kmemleak to detect the problem.

-Sumit

>
> 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