On Wed, 26 Jul 2023 at 13:49, Masahisa Kojima masahisa.kojima@linaro.org wrote:
Hi Ilias,
On Mon, 24 Jul 2023 at 19:22, Ilias Apalodimas ilias.apalodimas@linaro.org wrote:
Hi Kojima-san,
On Mon, 24 Jul 2023 at 05:53, Masahisa Kojima masahisa.kojima@linaro.org wrote:
Hi Ilias, Jan,
On Fri, 23 Jun 2023 at 03:56, Ilias Apalodimas ilias.apalodimas@linaro.org wrote:
Hi Kojima-san, Jan
On Thu, Jun 22, 2023 at 04:58:50PM +0200, Jan Kiszka wrote:
On 22.06.23 10:51, Masahisa Kojima wrote:
efivar operation is updated when the tee_stmm_efi module is probed. tee_stmm_efi module supports SetVariable runtime service, but user needs to manually remount the efivarfs as RW to enable the write access if the previous efivar operation does not support SerVariable and efivarfs is mounted as read-only.
This commit notifies the update of efivar operation to efivarfs subsystem, then drops SB_RDONLY flag if the efivar operation supports SetVariable.
But it does not re-add it and prevents further requests to the TA (that will only cause panics there) when the daemon terminates, does it?
It doesn't, but I think I got a better way out. Even what you suggest won't solve the problem entirely. For the sake of context
- The kernel decides between the RO/RW depending on the SetVariable ptr
- The stmm *module* registers and swaps the RT calls -- and the ptr is now
valid. Note here that the module probe function will run only if the supplicant is running
- Once the module is inserted the filesystem will be remounted even without
the supplicant running, which would not trigger an oops, but an hard to decipher error message from OP-TEE.
So even if we switch the permissions back to RO when the supplicant dies, someone can still remount it as RW and trigger the same error.
Which got me thinking and staring the TEE subsystem a bit more. The supplicant is backed by a /dev file, which naturally has .open() and .release() callbacks. Why don't we leave the module perform the initial setup -- e.g talk to StMM and make sure it's there, setup the necessary buffers etc and defer the actual swapping of the efivar ops and the filesystem permissions there? I might 'feel' a bit weird, but as I mentioned the module probe function only runs if the supplicant is running anyway
I think we are discussing two issues.
Yes
- efivar ops is not restored when the tee-supplicant daemon terminates.
The patch[1] sent by Sumit addresses this issue. Thanks to this patch, 'remove' callback of tee_stmm_efi_driver is called when the tee-supplicant daemon terminates, then restore the previous efivar ops and SB_RDONLY flag if necessary.
Ok but that didn't fix the original error Jan reported and I am not sure about the patch status
I think the patch is pending because the fTPM still causes panic when the system shuts down. https://lore.kernel.org/all/452472c5-ef30-ac30-6e4e-954f53b48315@siemens.com...
This is fTPM specific issue and is unrelated to the tee-based SetVariable runtime series itself.
- cause panic when someone remounts the efivarfs as RW even if
SetVariable is not supported.
Yes, this [0] is fixing that issue
Thank you, I will include this patch in the next submission.
Anyway, the GetVariable() runtime service backed by the U-Boot variable service does not work from kernel v6.4.0, so I will investigate this issue.
I found that the QueryVariableInfo EFI API is required since this patch[2]. Current U-Boot does not support QueryVariableInfo runtime service. Anyway this is not directly related to this series. After efivar ops is replaced by the tee-based one, variable access works fine.
[2] https://lore.kernel.org/all/20230517153812.2010174-1-anisse@astier.eu/
Thanks, Masahisa Kojima
Thanks, Masahisa Kojima
[0] https://lore.kernel.org/linux-efi/20230609094532.562934-1-ilias.apalodimas@l... Thanks /Ilias
[1] https://lore.kernel.org/all/20230607151435.92654-1-sumit.garg@linaro.org/
Thanks, Masahisa Kojima
Cheers /Ilias
Jan
-- Siemens AG, Technology Competence Center Embedded Linux