Re: [PATCH bpf-next v3] bpf: crypto: Use AES-CBC and AES-ECB libraries

[Eric Biggers <ebiggers@kernel.org>]

On Tue, Sep 22, 2026 at 04:48:02AM +0000, Alexei Starovoitov wrote:
> On Mon, Sep 21, 2026 at 09:04 PM Eric Biggers <ebiggers@kernel.org> wrote:
> > +config BPF_CRYPTO
> > +	def_bool y
> > +	depends on BPF_SYSCALL
> > +	depends on CRYPTO_LIB_AES_CBC
> > +	depends on CRYPTO_LIB_AES_ECB
> 
> This will break the build with CRYPTO_AES=m.

No, the new implementation only calls library code.  And if that library
code isn't built-in, then this just doesn't get built at all, as per the
'depends on' lines.

I'm not sure what you expected.  This could be a tristate, but that
would mean it would be its own module, which doesn't seem conventional
for kfuncs.

> >  struct bpf_crypto_ctx {
> > -	const struct bpf_crypto_type *type;
> > -	void *tfm;
> > -	u32 siv_len;
> > +	enum bpf_crypto_algo_id algo;
> > +	void *key;
> 
> No need for this. The bot was wrong.
> Reading any field of struct bpf_crypto_ctx requires CAP_PERFMON.

Okay, it sounded like a weird BPF quirk where the type system was being
used to enforce a security boundary.  But if it's not needed, then
that's helpful.  I'll go back to the original struct embedding.

- Eric