Re: [PATCH] optee: Suppress false positive kmemleak report in optee_handle_rpc()

[Wang, Xiaolei]

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@xxxxxxxxxxxxx>
> > ---
> >   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