Messages in this thread | | | From | Dan Williams <> | Date | Mon, 18 Mar 2019 18:34:02 -0700 | Subject | Re: [PATCH] security/keys/trusted: Allow operation without hardware TPM |
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On Mon, Mar 18, 2019 at 5:56 PM James Bottomley <jejb@linux.ibm.com> wrote: > > On Mon, 2019-03-18 at 17:30 -0700, Dan Williams wrote: > > On Mon, Mar 18, 2019 at 5:24 PM James Bottomley <jejb@linux.ibm.com> > > wrote: > > > > > > On Mon, 2019-03-18 at 16:45 -0700, Dan Williams wrote: > > > > Rather than fail initialization of the trusted.ko module, arrange > > > > for the module to load, but rely on trusted_instantiate() to fail > > > > trusted-key operations. > > > > > > What actual problem is this fixing? To me it would seem like an > > > enhancement to make the trusted module fail at load time if there's > > > no TPM rather than waiting until first use to find out it can never > > > work. Is there some piece of user code that depends on the > > > successful insertion of trusted.ko? > > > > The module dependency chain relies on it. If that can be broken that > > would also be an acceptable fix. > > > > I found this through the following dependency chain: libnvdimm.ko -> > > encrypted_keys.ko -> trusted.ko. > > > > "key_type_trusted" is the symbol that encrypted_keys needs regardless > > of whether the tpm is present. > > That's a nasty dependency caused by every key type module exporting a > symbol for its key type. It really seems that key types should be > looked up by name not symbol to prevent more of these dependency issues > from spreading. Something like this (untested and definitely won't > work without doing an EXPORT_SYMBOL on key_type_lookup). > > If it does look acceptable we can also disentangle the nasty module > dependencies in the encrypted key code around masterkey which alone > should be a huge improvement because that code is too hacky to live.
Looks good to me. I fired it up with the export added and also included a:
MODULE_SOFTDEP("pre: trusted");
...to encourage trusted.ko to be ready, if possible, for the lookup.
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