Re: [PATCH v2] KEYS: trusted: Debugging as a feature

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Mar 26, 2026 at 10:34:58PM +0530, Srish Srinivasan wrote:
> 
> On 3/24/26 4:30 PM, Jarkko Sakkinen wrote:
> > TPM_DEBUG, and other similar flags, are a non-standard way to specify a
> > feature in Linux kernel.  Introduce CONFIG_TRUSTED_KEYS_DEBUG for
> > trusted keys, and use it to replace these ad-hoc feature flags.
> > 
> > Given that trusted keys debug dumps can contain sensitive data, harden
> > the feature as follows:
> > 
> > 1. In the Kconfig description postulate that pr_debug() statements must be
> >     used.
> > 2. Use pr_debug() statements in TPM 1.x driver to print the protocol dump.
> > 
> > Traces, when actually needed, can be easily enabled by providing
> > trusted.dyndbg='+p' in the kernel command-line.
> > 
> > Cc: Srish Srinivasan <ssrish@linux.ibm.com>
> > Reported-by: Nayna Jain <nayna@linux.ibm.com>
> > Closes: https://lore.kernel.org/all/7f8b8478-5cd8-4d97-bfd0-341fd5cf10f9@linux.ibm.com/
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> 
> 
> Tested on PKWM and emulated TPM backends.
> 
> Tested-by: Srish Srinivasan <ssrish@linux.ibm.com>

Thank you!

As it is uprised as a feature (like it should as ad-hoc compilation
flags are harmful), this also requires a boot flag so that "I know
what I'm doing" is addressed.

I'll send one more round with a flag 'trusted.debug=0|1'. These extra
steps protect production kernels for reasonable measure.

BR, Jarkko