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

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Date:   Wed, 15 Dec 2021 21:33:14 +0800
From:   "Wang, Xiaolei" <xiaolei.wang@...driver.com>
To:     Jens Wiklander <jens.wiklander@...aro.org>
Cc:     sumit.garg@...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()


在 12/15/2021 8:29 PM, Jens Wiklander 写道:
> [Please note: This e-mail is from an EXTERNAL e-mail address]
>
> On Mon, Dec 06, 2021 at 08:05:33PM +0800, Xiaolei Wang 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.
>>
>> Signed-off-by: Xiaolei Wang <xiaolei.wang@...driver.com>
>> ---
>>   drivers/tee/optee/smc_abi.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
>> index 6196d7c3888f..cf2e3293567d 100644
>> --- a/drivers/tee/optee/smc_abi.c
>> +++ b/drivers/tee/optee/smc_abi.c
>> @@ -23,6 +23,7 @@
>>   #include "optee_private.h"
>>   #include "optee_smc.h"
>>   #include "optee_rpc_cmd.h"
>> +#include <linux/kmemleak.h>
>>   #define CREATE_TRACE_POINTS
>>   #include "optee_trace.h"
>>
>> @@ -783,6 +784,7 @@ static void optee_handle_rpc(struct tee_context *ctx,
>>                        param->a4 = 0;
>>                        param->a5 = 0;
>>                }
>> +             kmemleak_not_leak(shm);
> Eventually this pointer will be freed below with the call to tee_shm_free().
> I assume than once the memory is freed it's not execused from being a leak
> any longer. Is that correct?

Yes, it is the correct way to release memory through tee_shm_free, but 
if a memory leak is detected by the kernel before free memory, it is 
obviously a false alarm.

thanks

xiaolei

>
> Thanks,
> Jens
>
>>                break;
>>        case OPTEE_SMC_RPC_FUNC_FREE:
>>                shm = reg_pair_to_ptr(param->a1, param->a2);
>> --
>> 2.25.1
>>