[RFC] integrity: wait for completion of i2c initialization using late_initcall_sync()

[Romain Naour]

From: Romain Naour <romain.naour at skf.com>

It has been reported that on some plateforms the ima and evm
initialization were performed too early during initcall initialization
process and misses TPM chip detection [1] [2].

Indeed, ima may uses a TPM chip but requires to wait for bus
interface (spi or i2c) and TPM driver initialization.

[    0.166261] ima: No TPM chip found, activating TPM-bypass!
...
[    0.166322] evm: Initialising EVM extended attributes:
...
[    0.182571] ti-sci 44083000.system-controller: ABI: 3.1 (firmware rev 0x0009 '9.2.4--v09.02.04 (Kool Koala)')
[    0.281540] omap_i2c 42120000.i2c: bus 0 rev0.12 at 400 kHz
[    0.282314] omap_i2c 2000000.i2c: bus 4 rev0.12 at 400 kHz
[    0.282972] omap_i2c 2010000.i2c: bus 5 rev0.12 at 400 kHz
[    0.335177] tpm_tis_i2c 2-002e: 2.0 TPM (device-id 0x1C, rev-id 22)
[    0.471596] omap_i2c 2020000.i2c: bus 2 rev0.12 at 100 kHz
[    0.472310] omap_i2c 2030000.i2c: bus 6 rev0.12 at 400 kHz
[    0.472951] omap_i2c 2040000.i2c: bus 3 rev0.12 at 100 kHz
[    0.473596] omap_i2c 2050000.i2c: bus 7 rev0.12 at 400 kHz
[    0.474274] omap_i2c 2060000.i2c: bus 1 rev0.12 at 100 kHz

The ima stack was expecting to start after the TPM device (hence the
comment) using late_initcall() but fail to do so on such plateforms:

  late_initcall(init_ima);	/* Start IMA after the TPM is available */

Using late_initcall_sync() variant allows to really wait for i2c
initialization completion.

[    0.285986] omap_i2c 42120000.i2c: bus 0 rev0.12 at 400 kHz
[    0.286706] omap_i2c 2000000.i2c: bus 4 rev0.12 at 400 kHz
[    0.287382] omap_i2c 2010000.i2c: bus 5 rev0.12 at 400 kHz
[    0.331503] tpm_tis_i2c 2-002e: 2.0 TPM (device-id 0x1C, rev-id 22)
[    0.677185] omap_i2c 2020000.i2c: bus 2 rev0.12 at 100 kHz
[    0.677904] omap_i2c 2030000.i2c: bus 6 rev0.12 at 400 kHz
[    0.678557] omap_i2c 2040000.i2c: bus 3 rev0.12 at 100 kHz
[    0.679167] omap_i2c 2050000.i2c: bus 7 rev0.12 at 400 kHz
[    0.679792] omap_i2c 2060000.i2c: bus 1 rev0.12 at 100 kHz
...
[    3.062788] ima: Allocated hash algorithm: sha256
...
[    3.318975] ima: No architecture policies found
[    3.323536] evm: Initialising EVM extended attributes:
[    3.328662] evm: security.selinux (disabled)
[    3.332919] evm: security.SMACK64 (disabled)
[    3.337177] evm: security.SMACK64EXEC (disabled)
[    3.341781] evm: security.SMACK64TRANSMUTE (disabled)
[    3.346819] evm: security.SMACK64MMAP (disabled)
[    3.351422] evm: security.apparmor (disabled)
[    3.355764] evm: security.ima
[    3.358721] evm: security.capability
[    3.362285] evm: HMAC attrs: 0x1

[1] https://lore.kernel.org/linux-integrity/9b98d912-ba78-402c-a5c8-154bef8794f7@smile.fr/
[2] https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1375425/tda4vm-ima-vs-tpm-builtin-driver-boot-order

Signed-off-by: Romain Naour <romain.naour at skf.com>
---
 security/integrity/evm/evm_main.c | 2 +-
 security/integrity/ima/ima_main.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 62fe66dd53ce..316f8d140825 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -1180,4 +1180,4 @@ DEFINE_LSM(evm) = {
 	.blobs = &evm_blob_sizes,
 };
 
-late_initcall(init_evm);
+late_initcall_sync(init_evm);	/* Start EVM after IMA */
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index f04f43af651c..0aa7cd9aabfa 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -1220,4 +1220,4 @@ DEFINE_LSM(ima) = {
 	.blobs = &ima_blob_sizes,
 };
 
-late_initcall(init_ima);	/* Start IMA after the TPM is available */
+late_initcall_sync(init_ima);	/* Start IMA after the TPM is available */
-- 
2.45.0