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Date: Tue, 14 Mar 2023 13:56:15 -0700
From: Jeffrey Kardatzke <jkardatzke@...omium.org>
To: Sumit Garg <sumit.garg@...aro.org>
Cc: op-tee@...ts.trustedfirmware.org,
Jens Wiklander <jens.wiklander@...aro.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6] tee: optee: Add SMC for loading OP-TEE image
On Tue, Mar 14, 2023 at 5:41 AM Sumit Garg <sumit.garg@...aro.org> wrote:
>
> On Mon, 13 Mar 2023 at 22:47, Jeffrey Kardatzke <jkardatzke@...omium.org> wrote:
> >
> > On Mon, Mar 13, 2023 at 1:03 AM Sumit Garg <sumit.garg@...aro.org> wrote:
> > >
> > > On Fri, 10 Mar 2023 at 01:13, Jeffrey Kardatzke <jkardatzke@...omium.org> wrote:
> > > >
> > > > Adds an SMC call that will pass an OP-TEE binary image to EL3 and
> > > > instruct it to load it as the BL32 payload. This works in conjunction
> > > > with a feature added to Trusted Firmware for ARMv8 and above
> > > > architectures that supports this.
> > > >
> > > > The main purpose of this change is to facilitate updating the OP-TEE
> > > > component on devices via a rootfs change rather than having to do a
> > > > firmware update. Further details are linked to in the Kconfig file.
> > > >
> > > > Signed-off-by: Jeffrey Kardatzke <jkardatzke@...omium.org>
> > > > Signed-off-by: Jeffrey Kardatzke <jkardatzke@...gle.com>
> > > > ---
> > > >
> > > > Changes in v6:
> > > > - Expanded Kconfig documentation
> > > >
> > > > Changes in v5:
> > > > - Renamed config option
> > > > - Added runtime warning when config is used
> > > >
> > > > Changes in v4:
> > > > - Update commit message
> > > > - Added more documentation
> > > > - Renamed config option, added ARM64 dependency
> > > >
> > > > Changes in v3:
> > > > - Removed state tracking for driver reload
> > > > - Check UID of service to verify it needs image load
> > > >
> > > > Changes in v2:
> > > > - Fixed compile issue when feature is disabled
> > > > - Addressed minor comments
> > > > - Added state tracking for driver reload
> > > >
> > > > drivers/tee/optee/Kconfig | 29 +++++++++++
> > > > drivers/tee/optee/optee_msg.h | 12 +++++
> > > > drivers/tee/optee/optee_smc.h | 24 +++++++++
> > > > drivers/tee/optee/smc_abi.c | 97 +++++++++++++++++++++++++++++++++++
> > > > 4 files changed, 162 insertions(+)
> > > >
> > > > diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig
> > > > index f121c224e682..8d4836c58486 100644
> > > > --- a/drivers/tee/optee/Kconfig
> > > > +++ b/drivers/tee/optee/Kconfig
> > > > @@ -7,3 +7,32 @@ config OPTEE
> > > > help
> > > > This implements the OP-TEE Trusted Execution Environment (TEE)
> > > > driver.
> > > > +
> > > > +config OPTEE_INSECURE_LOAD_IMAGE
> > > > + bool "Load OP-TEE image as firmware"
> > > > + default n
> > > > + depends on OPTEE && ARM64
> > > > + help
> > > > + This loads the BL32 image for OP-TEE as firmware when the driver is
> > > > + probed. This returns -EPROBE_DEFER until the firmware is loadable from
> > > > + the filesystem which is determined by checking the system_state until
> > > > + it is in SYSTEM_RUNNING. This also requires enabling the corresponding
> > > > + option in Trusted Firmware for Arm. The documentation there explains
> > > > + the security threat associated with enabling this as well as
> > > > + mitigations at the firmware and platform level.
> > > > + https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_model.html
> > > > +
> > > > + When utilizing this option, the following mitigations should be
> > > > + implemented to prevent attacks at the kernel level.
> > > > + 1. There must be boot chain security that verifies the kernel and
> > > > + rootfs, otherwise an attacker can modify the loaded OP-TEE binary.
> > > > + 2. It is recommended to build it as an included driver rather than
> > > > + a module to prevent exploits that may cause the module to not be
> > > > + loaded.
> > > > + 3. If there are alternate methods of booting the device, such as a
> > > > + recovery mode, it should be ensured that the same mitigations are
> > > > + applied in that mode.
> > > > + 4. The OP-TEE driver must be loaded before any potential attack
> > > > + vectors are opened up. This should include mounting of any
> > > > + modifiable filesystems, opening of network ports or communicating
> > > > + with external devices (such a USB).
> > >
> > > This detailed threat model documentation belongs here [1] and it
> > > should rather be in following format for every bullet point:
> > >
> > > Attack vector: <>
> > > Mitigation: <>
> > >
> > > [1] https://docs.kernel.org/staging/tee.html?highlight=tee#op-tee-driver
> > >
> >
> > Done in v7 patch set.
> >
> > > > diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.h
> > > > index 70e9cc2ee96b..e8840a82b983 100644
> > > > --- a/drivers/tee/optee/optee_msg.h
> > > > +++ b/drivers/tee/optee/optee_msg.h
> > > > @@ -241,11 +241,23 @@ struct optee_msg_arg {
> > > > * 384fb3e0-e7f8-11e3-af63-0002a5d5c51b.
> > > > * Represented in 4 32-bit words in OPTEE_MSG_UID_0, OPTEE_MSG_UID_1,
> > > > * OPTEE_MSG_UID_2, OPTEE_MSG_UID_3.
> > > > + *
> > > > + * In the case where the OP-TEE image is loaded by the kernel, this will
> > > > + * initially return an alternate UID to reflect that we are communicating with
> > > > + * the TF-A image loading service at that time instead of OP-TEE. That UID is:
> > > > + * a3fbeab1-1246-315d-c7c4-06b9c03cbea4.
> > > > + * Represented in 4 32-bit words in OPTEE_MSG_IMAGE_LOAD_UID_0,
> > > > + * OPTEE_MSG_IMAGE_LOAD_UID_1, OPTEE_MSG_IMAGE_LOAD_UID_2,
> > > > + * OPTEE_MSG_IMAGE_LOAD_UID_3.
> > > > */
> > > > #define OPTEE_MSG_UID_0 0x384fb3e0
> > > > #define OPTEE_MSG_UID_1 0xe7f811e3
> > > > #define OPTEE_MSG_UID_2 0xaf630002
> > > > #define OPTEE_MSG_UID_3 0xa5d5c51b
> > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_0 0xa3fbeab1
> > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_1 0x1246315d
> > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_2 0xc7c406b9
> > > > +#define OPTEE_MSG_IMAGE_LOAD_UID_3 0xc03cbea4
> > > > #define OPTEE_MSG_FUNCID_CALLS_UID 0xFF01
> > > >
> > > > /*
> > > > diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> > > > index 73b5e7760d10..7d9fa426505b 100644
> > > > --- a/drivers/tee/optee/optee_smc.h
> > > > +++ b/drivers/tee/optee/optee_smc.h
> > > > @@ -104,6 +104,30 @@ struct optee_smc_call_get_os_revision_result {
> > > > unsigned long reserved1;
> > > > };
> > > >
> > > > +/*
> > > > + * Load Trusted OS from optee/tee.bin in the Linux firmware.
> > > > + *
> > > > + * WARNING: Use this cautiously as it could lead to insecure loading of the
> > > > + * Trusted OS.
> > > > + * This SMC instructs EL3 to load a binary and execute it as the Trusted OS.
> > > > + *
> > > > + * Call register usage:
> > > > + * a0 SMC Function ID, OPTEE_SMC_CALL_LOAD_IMAGE
> > > > + * a1 Upper 32bit of a 64bit size for the payload
> > > > + * a2 Lower 32bit of a 64bit size for the payload
> > > > + * a3 Upper 32bit of the physical address for the payload
> > > > + * a4 Lower 32bit of the physical address for the payload
> > > > + *
> > > > + * The payload is in the OP-TEE image format.
> > > > + *
> > > > + * Returns result in a0, 0 on success and an error code otherwise.
> > > > + */
> > > > +#define OPTEE_SMC_FUNCID_LOAD_IMAGE 2
> > > > +#define OPTEE_SMC_CALL_LOAD_IMAGE \
> > > > + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
> > > > + ARM_SMCCC_OWNER_TRUSTED_OS_END, \
> > > > + OPTEE_SMC_FUNCID_LOAD_IMAGE)
> > > > +
> > > > /*
> > > > * Call with struct optee_msg_arg as argument
> > > > *
> > > > diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
> > > > index a1c1fa1a9c28..00b6b69b6f79 100644
> > > > --- a/drivers/tee/optee/smc_abi.c
> > > > +++ b/drivers/tee/optee/smc_abi.c
> > > > @@ -8,9 +8,11 @@
> > > >
> > > > #include <linux/arm-smccc.h>
> > > > #include <linux/errno.h>
> > > > +#include <linux/firmware.h>
> > > > #include <linux/interrupt.h>
> > > > #include <linux/io.h>
> > > > #include <linux/irqdomain.h>
> > > > +#include <linux/kernel.h>
> > > > #include <linux/mm.h>
> > > > #include <linux/module.h>
> > > > #include <linux/of.h>
> > > > @@ -1149,6 +1151,22 @@ static bool optee_msg_api_uid_is_optee_api(optee_invoke_fn *invoke_fn)
> > > > return false;
> > > > }
> > > >
> > > > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> > > > +static bool optee_msg_api_uid_is_optee_image_load(optee_invoke_fn *invoke_fn)
> > > > +{
> > > > + struct arm_smccc_res res;
> > > > +
> > > > + invoke_fn(OPTEE_SMC_CALLS_UID, 0, 0, 0, 0, 0, 0, 0, &res);
> > > > +
> > > > + if (res.a0 == OPTEE_MSG_IMAGE_LOAD_UID_0 &&
> > > > + res.a1 == OPTEE_MSG_IMAGE_LOAD_UID_1 &&
> > > > + res.a2 == OPTEE_MSG_IMAGE_LOAD_UID_2 &&
> > > > + res.a3 == OPTEE_MSG_IMAGE_LOAD_UID_3)
> > > > + return true;
> > > > + return false;
> > > > +}
> > > > +#endif
> > > > +
> > > > static void optee_msg_get_os_revision(optee_invoke_fn *invoke_fn)
> > > > {
> > > > union {
> > > > @@ -1354,6 +1372,81 @@ static void optee_shutdown(struct platform_device *pdev)
> > > > optee_disable_shm_cache(optee);
> > > > }
> > > >
> > > > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE
> > > > +
> > > > +#define OPTEE_FW_IMAGE "optee/tee.bin"
> > > > +
> > > > +static int optee_load_fw(struct platform_device *pdev,
> > > > + optee_invoke_fn *invoke_fn)
> > > > +{
> > > > + const struct firmware *fw = NULL;
> > > > + struct arm_smccc_res res;
> > > > + phys_addr_t data_pa;
> > > > + u8 *data_buf = NULL;
> > > > + u64 data_size;
> > > > + u32 data_pa_high, data_pa_low;
> > > > + u32 data_size_high, data_size_low;
> > > > + int rc;
> > > > +
> > > > + if (!optee_msg_api_uid_is_optee_image_load(invoke_fn))
> > > > + return 0;
> > > > +
> > > > + rc = request_firmware(&fw, OPTEE_FW_IMAGE, &pdev->dev);
> > > > + if (rc) {
> > > > + /*
> > > > + * The firmware in the rootfs will not be accessible until we
> > > > + * are in the SYSTEM_RUNNING state, so return EPROBE_DEFER until
> > > > + * that point.
> > > > + */
> > > > + if (system_state < SYSTEM_RUNNING)
> > > > + return -EPROBE_DEFER;
> > > > + goto fw_err;
> > > > + }
> > > > +
> > > > + data_size = fw->size;
> > > > + /*
> > > > + * This uses the GFP_DMA flag to ensure we are allocated memory in the
> > > > + * 32-bit space since TF-A cannot map memory beyond the 32-bit boundary.
> > > > + */
> > > > + data_buf = kmalloc(fw->size, GFP_KERNEL | GFP_DMA);
> > > > + if (!data_buf) {
> > > > + rc = -ENOMEM;
> > > > + goto fw_err;
> > > > + }
> > > > + memcpy(data_buf, fw->data, fw->size);
> > > > + data_pa = virt_to_phys(data_buf);
> > > > + reg_pair_from_64(&data_pa_high, &data_pa_low, data_pa);
> > > > + reg_pair_from_64(&data_size_high, &data_size_low, data_size);
> > > > + goto fw_load;
> > > > +
> > > > +fw_err:
> > > > + pr_warn("image loading failed\n");
> > > > + data_pa_high = data_pa_low = data_size_high = data_size_low = 0;
> > > > +
> > > > +fw_load:
> > > > + /*
> > > > + * Always invoke the SMC, even if loading the image fails, to indicate
> > > > + * to EL3 that we have passed the point where it should allow invoking
> > > > + * this SMC.
> > > > + */
> > > > + pr_warn("OP-TEE image loaded from kernel, this can be insecure");
> > > > + invoke_fn(OPTEE_SMC_CALL_LOAD_IMAGE, data_size_high, data_size_low,
> > > > + data_pa_high, data_pa_low, 0, 0, 0, &res);
> > >
> > > Apart from the security considerations discussed, I see an issue with
> > > the implementation here. Here you only initialize OP-TEE on *CPUX*
> > > that is performing OP-TEE probe. IIRC, it is required for that CPUX to
> > > be primary CPU0. How do we ensure that here?
> >
> > I'm not aware of any restrictions that require OP-TEE to be loaded on
> > CPU0, do you have a point to something that indicates such a
> > requirement? (it's always worked fine for me no matter what core it
> > inits on)
>
> You can grep in OP-TEE OS code base for keywords like "primary" and
> "secondary". This will give you an idea how initialization differs
> among primary and secondary CPUs.
Yes, I can see there are different things for "primary" vs.
"secondary", but what I'm not seeing is anything that indicates that
"primary" must be core 0 and not just the first CPU that boots into
OP-TEE. Can you point me to anything that establishes that
requirement?
>I would be interested to see the
> OP-TEE init log (LOG_LEVEL = 4) when the primary CPU is *not* CPU0.
> You can try to force that environment using taskset [1] while
> installing the OP-TEE module as an out-of-tree build.
OK, here's the log from booting up with that. I changed the log line
for "Primary CPU initializing" to include the core #.
D/TC:6 plat_get_aslr_seed:111 Warning: no ASLR seed
D/TC:6 add_phys_mem:635 ROUNDDOWN(0x0C000000 + 0x400000,
CORE_MMU_PGDIR_SIZE) type IO_SEC 0x0c400000 size 0x00200000
D/TC:6 add_phys_mem:635 ROUNDDOWN(0x0C000000 + 0x0,
CORE_MMU_PGDIR_SIZE) type IO_SEC 0x0c000000 size 0x00200000
D/TC:6 add_phys_mem:635 ROUNDDOWN(0x11001100, CORE_MMU_PGDIR_SIZE)
type IO_NSEC 0x11000000 size 0x00200000
D/TC:6 add_phys_mem:635 TEE_SHMEM_START type NSEC_SHM 0x43c00000
size 0x00200000
D/TC:6 add_phys_mem:635 TA_RAM_START type TA_RAM 0x43400000 size 0x00800000
D/TC:6 add_phys_mem:635 VCORE_UNPG_RW_PA type TEE_RAM_RW 0x4325c000
size 0x001a4000
D/TC:6 add_phys_mem:635 VCORE_UNPG_RX_PA type TEE_RAM_RX 0x43200000
size 0x0005c000
D/TC:6 add_va_space:675 type RES_VASPACE size 0x00a00000
D/TC:6 add_va_space:675 type SHM_VASPACE size 0x02000000
D/TC:6 dump_mmap_table:800 type TEE_RAM_RX va
0x43200000..0x4325bfff pa 0x43200000..0x4325bfff size 0x0005c000
(smallpg)
D/TC:6 dump_mmap_table:800 type TEE_RAM_RW va
0x4325c000..0x433fffff pa 0x4325c000..0x433fffff size 0x001a4000
(smallpg)
D/TC:6 dump_mmap_table:800 type SHM_VASPACE va
0x43400000..0x453fffff pa 0x00000000..0x01ffffff size 0x02000000
(pgdir)
D/TC:6 dump_mmap_table:800 type RES_VASPACE va
0x45400000..0x45dfffff pa 0x00000000..0x009fffff size 0x00a00000
(pgdir)
D/TC:6 dump_mmap_table:800 type IO_SEC va
0x45e00000..0x45ffffff pa 0x0c000000..0x0c1fffff size 0x00200000
(pgdir)
D/TC:6 dump_mmap_table:800 type IO_SEC va
0x46000000..0x461fffff pa 0x0c400000..0x0c5fffff size 0x00200000
(pgdir)
D/TC:6 dump_mmap_table:800 type IO_NSEC va
0x46200000..0x463fffff pa 0x11000000..0x111fffff size 0x00200000
(pgdir)
D/TC:6 dump_mmap_table:800 type TA_RAM va
0x46400000..0x46bfffff pa 0x43400000..0x43bfffff size 0x00800000
(pgdir)
D/TC:6 dump_mmap_table:800 type NSEC_SHM va
0x46c00000..0x46dfffff pa 0x43c00000..0x43dfffff size 0x00200000
(pgdir)
D/TC:6 core_mmu_xlat_table_alloc:526 xlat tables used 1 / 5
D/TC:6 core_mmu_xlat_table_alloc:526 xlat tables used 2 / 5
I/TC:
D/TC:6 0 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
workaround enabled with "K" = 32
I/TC: OP-TEE version: Unknown_3.18 (gcc version 11.2.0 (coreboot
toolchain v_)) #1 Tue Mar 14 18:08:58 UTC 2023 aarch64
I/TC: WARNING: This OP-TEE configuration might be insecure!
I/TC: WARNING: Please check
https://optee.readthedocs.io/en/latest/architecture/porting_guidelines.html
I/TC: Primary CPU 6 initializing
D/TC:6 0 boot_init_primary_late:1314 Executing at offset 0 with
virtual load address 0x43200000
D/TC:6 0 call_preinitcalls:21 level 2 mobj_mapped_shm_init()
D/TC:6 0 mobj_mapped_shm_init:463 Shared memory address range:
43400000, 45400000
D/TC:6 0 call_initcalls:40 level 1 register_time_source()
D/TC:6 0 call_initcalls:40 level 1 teecore_init_pub_ram()
D/TC:6 0 call_initcalls:40 level 3 check_ta_store()
D/TC:6 0 check_ta_store:408 TA store: "Secure Storage TA"
D/TC:6 0 check_ta_store:408 TA store: "REE"
D/TC:6 0 call_initcalls:40 level 3 verify_pseudo_tas_conformance()
D/TC:6 0 call_initcalls:40 level 3 tee_cryp_init()
D/TC:6 0 call_initcalls:40 level 4 tee_fs_init_key_manager()
D/TC:6 0 call_initcalls:40 level 6 mobj_init()
D/TC:6 0 call_initcalls:40 level 6 default_mobj_init()
I/TC: Primary CPU switching to normal world boot
D/TC:6 tee_entry_exchange_capabilities:100 Asynchronous
notifications are disabled
D/TC:6 tee_entry_exchange_capabilities:109 Dynamic shared memory is enabled
D/TC:6 0 core_mmu_xlat_table_alloc:526 xlat tables used 3 / 5
D/TC:? 0 tee_ta_init_pseudo_ta_session:296 Lookup pseudo TA
7011a688-ddde-4053-a5a9-7b3c4ddf13b8
D/TC:? 0 tee_ta_init_pseudo_ta_session:309 Open device.pta
D/TC:? 0 tee_ta_init_pseudo_ta_session:326 device.pta :
7011a688-ddde-4053-a5a9-7b3c4ddf13b8
F/TC:? 0 plat_prng_add_jitter_entropy:72 0xAC2D
D/TC:? 0 tee_ta_close_session:511 csess 0x43289a10 id 1
D/TC:? 0 tee_ta_close_session:530 Destroy session
I/TC: Secondary CPU 4 initializing
D/TC:4 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
workaround enabled with "K" = 32
I/TC: Secondary CPU 4 switching to normal world boot
D/TC:? 0 tee_ta_init_pseudo_ta_session:296 Lookup pseudo TA
a92d116c-ce27-4917-b30c-4a416e2d9351
D/TC:? 0 ldelf_load_ldelf:96 ldelf load address 0x80006000
D/LD: ldelf:134 Loading TS a92d116c-ce27-4917-b30c-4a416e2d9351
F/TC:? 0 trace_syscall:151 syscall #3 (syscall_get_property)
F/TC:? 0 trace_syscall:151 syscall #5 (syscall_open_ta_session)
D/TC:? 0 ldelf_syscall_open_bin:142 Lookup user TA ELF
a92d116c-ce27-4917-b30c-4a416e2d9351 (Secure Storage TA)
D/TC:? 1 tee_ta_init_session_with_context:606 Re-open TA
7011a688-ddde-4053-a5a9-7b3c4ddf13b8
F/TC:? 1 plat_prng_add_jitter_entropy:72 0xFC
D/TC:? 1 tee_ta_close_session:511 csess 0x43288b40 id 2
D/TC:? 1 tee_ta_close_session:530 Destroy session
F/TC:? 0 plat_prng_add_jitter_entropy:72 0x16
F/TC:? 0 plat_prng_add_jitter_entropy:72 0x36
F/TC:? 0 plat_prng_add_jitter_entropy:72 0x23
D/TC:? 0 ldelf_syscall_open_bin:146 res=0xffff0008
D/TC:? 0 ldelf_syscall_open_bin:142 Lookup user TA ELF
a92d116c-ce27-4917-b30c-4a416e2d9351 (REE)
I/TC: Secondary CPU 1 initializing
I/TC: Secondary CPU 1 switching to normal world boot
I/TC: Secondary CPU 5 initializing
D/TC:5 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
workaround enabled with "K" = 32
I/TC: Secondary CPU 5 switching to normal world boot
I/TC: Secondary CPU 2 initializing
I/TC: Secondary CPU 2 switching to normal world boot
I/TC: Secondary CPU 0 initializing
I/TC: Secondary CPU 0 switching to normal world boot
D/TC:? 0 ldelf_syscall_open_bin:146 res=0
F/TC:? 0 trace_syscall:151 syscall #7 (syscall_invoke_ta_command)
F/TC:? 0 trace_syscall:151 syscall #11 (syscall_mask_cancellation)
F/TC:? 0 trace_syscall:151 syscall #7 (syscall_invoke_ta_command)
F/TC:? 0 trace_syscall:151 syscall #3 (syscall_get_property)
F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
F/TC:? 0 plat_prng_add_jitter_entropy:72 0x9B
I/TC: Secondary CPU 7 initializing
D/TC:7 select_vector_wa_spectre_bhb:650 Spectre-BHB CVE-2022-23960
workaround enabled with "K" = 32
I/TC: Secondary CPU 7 switching to normal world boot
F/TC:? 0 plat_prng_add_jitter_entropy:72 0x31
F/TC:? 0 plat_prng_add_jitter_entropy:72 0xB6
I/TC: Secondary CPU 3 initializing
I/TC: Secondary CPU 3 switching to normal world boot
F/TC:? 0 plat_prng_add_jitter_entropy:72 0x23
F/TC:? 0 trace_syscall:151 syscall #6 (syscall_close_ta_session)
F/TC:? 0 trace_syscall:151 syscall #3 (syscall_get_property)
D/LD: ldelf:168 ELF (a92d116c-ce27-4917-b30c-4a416e2d9351) at 0x80049000
F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
F/TC:? 0 trace_syscall:151 syscall #8 (syscall_check_access_rights)
F/TC:? 0 trace_syscall:151 syscall #4 (syscall_get_property_name_to_index)
F/TC:? 0 plat_prng_add_jitter_entropy:72 0x38
>
> The one thing that essentially pops out to me is that, with the
> default SPI interrupt routing model (routed to CPU0), OP-TEE won't be
> able to handle the secure interrupts until it has been initialized on
> CPU0.
>
OK, so the actual concern is that we should initialize on all online
CPUs at startup or we may miss S-EL1 interrupts, correct?
> [1] https://man7.org/linux/man-pages/man1/taskset.1.html
>
> > >
> > > Also, I observe from the TF-A patch that you are doing lazy OP-TEE
> > > initialization for other secondary CPUs. IOW, if there is an OP-TEE
> > > SMC call invoked for a particular CPU then only you invoke
> > > opteed_cpu_on_finish_handler(0) once. This can be a bit unsafe as
> > > OP-TEE hasn't setup its context for those CPU which may involve some
> > > CPU specific security bits too such as:
> > > - GIC CPU interface initialization, secure vs non-secure interrupts.
> > > - Any platform and CPU specific TrustZone configuration.
> >
> > When opteed_cpu_on_finish_handler(0) is invoked...that invokes
> > opteed_init_optee_ep_state(...) which then sets up the CPU context for
> > that CPU. It then invokes opteed_synchronous_sp_entry for the
> > cpu_on_entry handler which should then do any other type of platform
> > specific initialization in the OP-TEE code itself. What setup in
> > OP-TEE are you referring to that isn't going to be invoked when doing
> > it the lazy way?
>
> No, I am not worried about any missing setup but rather deferred
> OP-TEE initialization for secondary CPUs after you open up the Linux
> attack surface.
What is the concern about initializing on secondary CPUs after the
attack surface is opened up?
>
> >
> > >
> > > I would have rather expected you to utilize cpuhp_setup_state() and
> > > friends to initialize OP-TEE for secondary CPUs during boot instead
> > > which is safe as per your platform threat model.
> > >
> > That could be another way to do it (I'm not familiar with that kernel
> > code currently)..
>
> AFAIK, there are many Linux kernel experts within Google who can guide
> you through.
>
I was simply stating that I wasn't familiar with that API...I have no
problems reading the API and understanding it myself. :)
> > but I'd rather stick with what I have unless there is
> > something technically wrong with it since it's already been approved
> > in TF-A.
>
> We can very well amend the TF-A implementation with a followup patch.
> Given above comments, the approach to initialize OP-TEE on all CPUs at
> once during boot should be the correct approach.
OK, so I've done this now in the v9 patchset. After it loads the
OP-TEE image, then it invokes cpuhp_setup_state(), which receives a
callback on each active core, which then simply gets the UID for
OP-TEE, and that invocation will then cause TF-A to init the context
for each core. Then it deregisters with cpuhp since that work is done.
This will then ensure that all cores that have come online will have
their CPU context initialized for OP-TEE. And any cores that may not
be online at this time will get initialized when they come back
online. This *should* address the concerns you have outlined above.
>
> -Sumit
>
> >
> > > -Sumit
> > >
> > > > + if (!rc)
> > > > + rc = res.a0;
> > > > + if (fw)
> > > > + release_firmware(fw);
> > > > + kfree(data_buf);
> > > > +
> > > > + return rc;
> > > > +}
> > > > +#else
> > > > +static inline int optee_load_fw(struct platform_device *__unused1,
> > > > + optee_invoke_fn *__unused2) {
> > > > + return 0;
> > > > +}
> > > > +#endif
> > > > +
> > > > static int optee_probe(struct platform_device *pdev)
> > > > {
> > > > optee_invoke_fn *invoke_fn;
> > > > @@ -1372,6 +1465,10 @@ static int optee_probe(struct platform_device *pdev)
> > > > if (IS_ERR(invoke_fn))
> > > > return PTR_ERR(invoke_fn);
> > > >
> > > > + rc = optee_load_fw(pdev, invoke_fn);
> > > > + if (rc)
> > > > + return rc;
> > > > +
> > > > if (!optee_msg_api_uid_is_optee_api(invoke_fn)) {
> > > > pr_warn("api uid mismatch\n");
> > > > return -EINVAL;
> > > > --
> > > > 2.40.0.rc1.284.g88254d51c5-goog
> > > >
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