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

Jens Wiklander
2021-05-06T07:02:54Z

On Wed, May 5, 2021 at 3:45 PM Allen Pais <apais@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@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