Re: [PATCH v2 1/2] optee: fix tee out of memory failure seen during kexec reboot

[Allen Pais <apais@linux.microsoft.com>]

>>>>>>>> 
>>>>>>>> I could not reproduce nor create a setup using QEMU, I could only
>>>>>>>> do it on a real h/w.
>>>>>>>> 
>>>>>>>> I have extensively tested the fix and I don't see any issues.
>>>>>>> 
>>>>>>> I did a few test runs too, seems OK.
>>>>>> 
>>>>>> I carried these changes and have not run into any issues with Kexec so far.
>>>>>> Last week, while trying out kdump, we ran into a crash(this is when the
>>>>>> Kdump kernel reboots).
>>>>>> 
>>>>>> $echo c > /proc/sysrq-trigger
>>>>>> 
>>>>>> Leads to:
>>>>>> 
>>>>>> [   18.004831] Unable to handle kernel paging request at virtual address ffff0008dcef6758
>>>>>> [   18.013002] Mem abort info:
>>>>>> [   18.015885]   ESR = 0x96000005
>>>>>> [   18.019034]   EC = 0x25: DABT (current EL), IL = 32 bits
>>>>>> [   18.024516]   SET = 0, FnV = 0
>>>>>> [   18.027667]   EA = 0, S1PTW = 0
>>>>>> [   18.030905] Data abort info:
>>>>>> [   18.033877]   ISV = 0, ISS = 0x00000005
>>>>>> [   18.037835]   CM = 0, WnR = 0
>>>>>> [   18.040896] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000970a78000
>>>>>> [   18.047811] [ffff0008dcef6758] pgd=000000097fbf9003, pud=0000000000000000
>>>>>> [   18.054819] Internal error: Oops: 96000005 [#1] SMP
>>>>>> [   18.059850] Modules linked in: bnxt_en pcie_iproc_platform pcie_iproc diagbe(O)
>>>>>> [   18.067395] CPU: 3 PID: 1 Comm: systemd-shutdow Tainted: G           O      5.4.83-microsoft-standard #1
>>>>>> [   18.077174] Hardware name: Overlake (DT)
>>>>>> [   18.081219] pstate: 80400005 (Nzcv daif +PAN -UAO)
>>>>>> [   18.086170] pc : tee_shm_free+0x18/0x48
>>>>>> [   18.090126] lr : optee_disable_shm_cache+0xa4/0xf0
>>>>>> [   18.095066] sp : ffff80001005bb90
>>>>>> [   18.098484] x29: ffff80001005bb90 x28: ffff000037e20000
>>>>>> [   18.103962] x27: 0000000000000000 x26: ffff00003ed10490
>>>>>> [   18.109440] x25: ffffca760e975f90 x24: 0000000000000000
>>>>>> [   18.114918] x23: ffffca760ed79808 x22: ffff00003ec66e18
>>>>>> [   18.120396] x21: ffff80001005bc08 x20: 00000000b200000a
>>>>>> [   18.125874] x19: ffff0008dcef6700 x18: 0000000000000010
>>>>>> [   18.131352] x17: 0000000000000000 x16: 0000000000000000
>>>>>> [   18.136829] x15: ffffffffffffffff x14: ffffca760ed79808
>>>>>> [   18.142307] x13: ffff80009005b897 x12: ffff80001005b89f
>>>>>> [   18.147786] x11: ffffca760eda4000 x10: ffff80001005b820
>>>>>> [   18.153264] x9 : 00000000ffffffd0 x8 : ffffca760e59b2c0
>>>>>> [   18.158742] x7 : 0000000000000000 x6 : 0000000000000000
>>>>>> [   18.164220] x5 : 0000000000000000 x4 : 0000000000000000
>>>>>> [   18.169698] x3 : 0000000000000000 x2 : ffff0008dcef6700
>>>>>> [   18.175175] x1 : 00000000ffff0008 x0 : ffffca760e59ca04
>>>>>> [   18.180654] Call trace:
>>>>>> [   18.183176]  tee_shm_free+0x18/0x48
>>>>>> [   18.186773]  optee_disable_shm_cache+0xa4/0xf0
>>>>>> [   18.191356]  optee_shutdown+0x20/0x30
>>>>>> [   18.195135]  platform_drv_shutdown+0x2c/0x38
>>>>>> [   18.199538]  device_shutdown+0x180/0x298
>>>>>> [   18.203586]  kernel_restart_prepare+0x44/0x50
>>>>>> [   18.208078]  kernel_restart+0x20/0x68
>>>>>> [   18.211853]  __do_sys_reboot+0x104/0x258
>>>>>> [   18.215899]  __arm64_sys_reboot+0x2c/0x38
>>>>>> [   18.220035]  el0_svc_handler+0x90/0x138
>>>>>> [   18.223991]  el0_svc+0x8/0x208
>>>>>> [   18.227143] Code: f9000bf3 aa0003f3 aa1e03e0 d503201f (b9405a60)
>>>>>> [   18.233435] ---[ end trace 835d756cd66aa959 ]---
>>>>>> [   18.238621] Kernel panic - not syncing: Fatal exception
>>>>>> [   18.244014] Kernel Offset: 0x4a75fde00000 from 0xffff800010000000
>>>>>> [   18.250299] PHYS_OFFSET: 0xffff99c680000000
>>>>>> [   18.254613] CPU features: 0x0002,21806008
>>>>>> [   18.258747] Memory Limit: none
>>>>>> [   18.262310] ---[ end Kernel panic - not syncing: Fatal exception ]—
>>>>>> 
>>>>>> I see that before secure world returns OPTEE_SMC_RETURN_ENOTAVAIL(which
>>>>>> Should disable and clear all the cache) we run into the crash trying to free shm.
>>>>>> 
>>>>>> Thoughts?
>>>>> 
>>>>> It seems that the pointer is invalid, but the pointer doesn't look
>>>>> like garbage. Could the kernel have unmapped the memory area covering
>>>>> that address?
>>>>> 
>>>> 
>>>> Yes, I am not entirely sure if the kernel had the time to unmap the memory.
>>>> Right after triggering the crash the kdump kernel is booted and I see the following
>>>> 
>>>> [ 2.050145] optee: probing for conduit method.
>>>> [ 2.054743] optee: revision 3.6 (f84427aa)
>>>> [ 2.054821] optee: dynamic shared memory is enabled
>>>> [ 2.066186] optee: initialized driver
>>>> 
>>>> Could this be previous un-released maps causing corruption?
>>> 
>>> Aha, yes, that could be it.
>>> 
>> 
>> How about checking for the ptr?
>> 
>> diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c
>> index aadedec3bfe7..8dc4fe9a1588 100644
>> --- a/drivers/tee/optee/call.c
>> +++ b/drivers/tee/optee/call.c
>> @@ -426,10 +426,12 @@ void optee_disable_shm_cache(struct optee *optee)
>>                if (res.result.status == OPTEE_SMC_RETURN_ENOTAVAIL)
>>                        break; /* All shm's freed */
>>                if (res.result.status == OPTEE_SMC_RETURN_OK) {
>> -                       struct tee_shm *shm;
>> +                       struct tee_shm *shm = NULL;
>> 
>>                        shm = reg_pair_to_ptr(res.result.shm_upper32,
>>                                              res.result.shm_lower32);
>> +                       if (IS_ERR(shm))
>> +                               return PTR_ERR(shm);
>>                        tee_shm_free(shm);
> 
> I don't think that will help. If your theory is correct then that
> pointer is from an older incarnation of the kernel. It could be worth
> trying calling this function just before the call to
> optee_enable_shm_cache() in optee_probe() but skipping the calls to
> `tee_shm_free()` in that case. Since the kernel has restarted these
> returned pointers are not valid any more and there's nothing to free,
> we just need to make sure that secure world stops using those too.
> 

Jens,

  I suppose you saw the email from @Tyler, we have it fixed but ran
Into many arm-smmu 64000000.mmu: xxx logs being printed out
And system becoming unstable and stops responding. 

 Am debugging this further, any input would be really helpful.

Thanks.