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

[Jens Wiklander]

On Wed, May 5, 2021 at 3:45 PM Allen Pais <apais at linux.microsoft.com> wrote:
>
> Jens,
>
> >>>> [    0.368428] tee_bnxt_fw optee-clnt0: tee_shm_alloc failed
> >>>> [    0.368461] tee_bnxt_fw: probe of optee-clnt0 failed with error -22
> >>>>
> >>>> tee_shm_release() is not invoked on dma shm buffer.
> >>>>
> >>>> Implement .shutdown() method to handle the release of the buffers
> >>>> correctly.
> >>>>
> >>>> More info:
> >>>> https://github.com/OP-TEE/optee_os/issues/3637
> >>>>
> >>>> Signed-off-by: Allen Pais <apais at linux.microsoft.com>
> >>>> ---
> >>>>  drivers/tee/optee/core.c | 20 ++++++++++++++++++++
> >>>>  1 file changed, 20 insertions(+)
> >>>
> >>> This looks good to me. Do you have a practical way of testing this on
> >>> QEMU for instance?
> >>>
> >>
> >> Jens,
> >>
> >>   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?

Cheers,
Jens