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Subject: Re: [PATCH v2 1/2] optee: fix tee out of memory failure seen during
 kexec reboot
From:   Allen Pais <apais@linux.microsoft.com>
In-Reply-To: <CAHUa44HTYcPyK95E+Mo2GNnCB9TfstA-n_4911JQh8V7-4vyjg@mail.gmail.com>
Date:   Thu, 6 May 2021 12:59:40 +0530
Cc:     Allen Pais <allen.lkml@gmail.com>, zajec5@gmail.com,
        bcm-kernel-feedback-list@broadcom.com,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        OP-TEE TrustedFirmware <op-tee@lists.trustedfirmware.org>
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References: <20210225090610.242623-1-allen.lkml@gmail.com>
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To:     Jens Wiklander <jens.wiklander@linaro.org>
Precedence: bulk

>>=20
>>>>>>>> [    0.368428] tee_bnxt_fw optee-clnt0: tee_shm_alloc failed
>>>>>>>> [    0.368461] tee_bnxt_fw: probe of optee-clnt0 failed with =
error -22
>>>>>>>>=20
>>>>>>>> tee_shm_release() is not invoked on dma shm buffer.
>>>>>>>>=20
>>>>>>>> Implement .shutdown() method to handle the release of the =
buffers
>>>>>>>> correctly.
>>>>>>>>=20
>>>>>>>> More info:
>>>>>>>> https://github.com/OP-TEE/optee_os/issues/3637
>>>>>>>>=20
>>>>>>>> Signed-off-by: Allen Pais <apais@linux.microsoft.com>
>>>>>>>> ---
>>>>>>>> drivers/tee/optee/core.c | 20 ++++++++++++++++++++
>>>>>>>> 1 file changed, 20 insertions(+)
>>>>>>>=20
>>>>>>> This looks good to me. Do you have a practical way of testing =
this on
>>>>>>> QEMU for instance?
>>>>>>>=20
>>>>>>=20
>>>>>> Jens,
>>>>>>=20
>>>>>> I could not reproduce nor create a setup using QEMU, I could only
>>>>>> do it on a real h/w.
>>>>>>=20
>>>>>> I have extensively tested the fix and I don't see any issues.
>>>>>=20
>>>>> I did a few test runs too, seems OK.
>>>>=20
>>>> 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).
>>>>=20
>>>> $echo c > /proc/sysrq-trigger
>>>>=20
>>>> Leads to:
>>>>=20
>>>> [   18.004831] Unable to handle kernel paging request at virtual =
address ffff0008dcef6758
>>>> [   18.013002] Mem abort info:
>>>> [   18.015885]   ESR =3D 0x96000005
>>>> [   18.019034]   EC =3D 0x25: DABT (current EL), IL =3D 32 bits
>>>> [   18.024516]   SET =3D 0, FnV =3D 0
>>>> [   18.027667]   EA =3D 0, S1PTW =3D 0
>>>> [   18.030905] Data abort info:
>>>> [   18.033877]   ISV =3D 0, ISS =3D 0x00000005
>>>> [   18.037835]   CM =3D 0, WnR =3D 0
>>>> [   18.040896] swapper pgtable: 4k pages, 48-bit VAs, =
pgdp=3D0000000970a78000
>>>> [   18.047811] [ffff0008dcef6758] pgd=3D000000097fbf9003, =
pud=3D0000000000000000
>>>> [   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 =
]=E2=80=94
>>>>=20
>>>> 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.
>>>>=20
>>>> Thoughts?
>>>=20
>>> 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?
>>>=20
>>=20
>> 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
>>=20
>> [ 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
>>=20
>> Could this be previous un-released maps causing corruption?
>=20
> Aha, yes, that could be it.
>=20

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 =3D=3D OPTEE_SMC_RETURN_ENOTAVAIL)
                        break; /* All shm's freed */
                if (res.result.status =3D=3D OPTEE_SMC_RETURN_OK) {
-                       struct tee_shm *shm;
+                       struct tee_shm *shm =3D NULL;
=20
                        shm =3D reg_pair_to_ptr(res.result.shm_upper32,
                                              res.result.shm_lower32);
+                       if (IS_ERR(shm))
+                               return PTR_ERR(shm);
                        tee_shm_free(shm);

Thanks.=