On Mon, 19 Jul 2021 at 12:40, Ahmad Fatoum [off-list ref] wrote:

Hello Andreas,

On 16.07.21 10:17, Andreas Rammhold wrote:

quoted

Before this commit the kernel could end up with no trusted key sources
even thought both of the currently supported backends (tpm & tee) were
compoiled as modules. This manifested in the trusted key type not being
registered at all.

I assume (TPM) trusted key module use worked before the TEE rework? If so,

an appropriate Fixes: Tag would then be in order.

quoted

When checking if a CONFIG_… preprocessor variable is defined we only
test for the builtin (=y) case and not the module (=m) case. By using
the IS_ENABLE(…) macro we to test for both cases.

It looks to me like you could now provoke a link error if TEE is a module
and built-in trusted key core tries to link against trusted_key_tee_ops.

That's true.

One solution for that IS_REACHABLE(). Another is to address the root cause,
which is the inflexible trusted keys Kconfig description:

- Trusted keys despite TEE support can still only be built when TCG_TPM is enabled
- There is no support to have TEE or TPM enabled without using those for
  enabled trusted keys as well
- As you noticed, module build of the backend has issues

I addressed these three issues in a patch[1], a month ago, but have yet to
receive feedback.

That's an oversight on my part since this patch was part of the new
CAAM trust source patch-set. Although I do admit that it was on my
TODO list. So I have provided some feedback on that patch. Can you
post the next version as an independent fix patch?

-Sumit

[1]: https://lore.kernel.org/linux-integrity/f8285eb0135ba30c9d846cf9dd395d1f5f8b1efc.1624364386.git-series.a.fatoum@pengutronix.de/ (local)

Cheers,
Ahmad

quoted

Signed-off-by: Andreas Rammhold <redacted>
---
 security/keys/trusted-keys/trusted_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index d5c891d8d353..fd640614b168 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c

@@ -27,10 +27,10 @@ module_param_named(source, trusted_key_source, charp, 0);
 MODULE_PARM_DESC(source, "Select trusted keys source (tpm or tee)");

 static const struct trusted_key_source trusted_key_sources[] = {
-#if defined(CONFIG_TCG_TPM)
+#if IS_ENABLED(CONFIG_TCG_TPM)
      { "tpm", &trusted_key_tpm_ops },
 #endif
-#if defined(CONFIG_TEE)
+#if IS_ENABLED(CONFIG_TEE)
      { "tee", &trusted_key_tee_ops },
 #endif
 };

--
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |