linux-kernel - Re: [PATCH bpf-next 2/3] bpf: Add a BPF helper for getting the IMA hash of an inode

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Message-ID: <CACYkzJ6bZBybX5tg2DvyJUkBPQ6_qP5FVKvMxdCe+CbA-OmPag@mail.gmail.com>
Date:   Sat, 21 Nov 2020 01:14:04 +0100
From:   KP Singh <kpsingh@...omium.org>
To:     Yonghong Song <yhs@...com>
Cc:     James Morris <jmorris@...ei.org>,
        open list <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        Linux Security Module list 
        <linux-security-module@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Florent Revest <revest@...omium.org>,
        Brendan Jackman <jackmanb@...omium.org>,
        Mimi Zohar <zohar@...ux.ibm.com>
Subject: Re: [PATCH bpf-next 2/3] bpf: Add a BPF helper for getting the IMA
 hash of an inode

[...]

> > + * long bpf_ima_inode_hash(struct inode *inode, void *dst, u32 size)
> > + *   Description
> > + *           Returns the stored IMA hash of the *inode* (if it's avaialable).
> > + *           If the hash is larger than *size*, then only *size*
> > + *           bytes will be copied to *dst*
> > + *   Return > + *            The **hash_algo** of is returned on success,
>
> of => if?

Just changed it to:

"The **hash_algo** is returned on success"

>
> > + *           **-EOPNOTSUP** if IMA is disabled and **-EINVAL** if
>
> and => or

Done. (and the same for tools/)

>

[...]

> > +     .gpl_only       = false,
> > +     .ret_type       = RET_INTEGER,
> > +     .arg1_type      = ARG_PTR_TO_BTF_ID,
> > +     .arg1_btf_id    = &bpf_ima_inode_hash_btf_ids[0],
> > +     .arg2_type      = ARG_PTR_TO_UNINIT_MEM,
> > +     .arg3_type      = ARG_CONST_SIZE_OR_ZERO,
>
> I know ARG_CONST_SIZE_OR_ZERO provides some flexibility and may
> make verifier easier to verify programs. But beyond that did
> you see any real use case user will pass a zero size buf to
> get hash value?
>

I agree, in this case it makes more sense to ARG_CONST_SIZE.

> > +     .allowed        = bpf_ima_inode_hash_allowed,
> > +};

[...]