RE: [PATCH v2 3/6] bpf-lsm: Introduce new helper bpf_ima_file_hash()

[Roberto Sassu]

> From: Yonghong Song [mailto:yhs@xxxxxx]
> Sent: Tuesday, February 15, 2022 6:03 PM
> On 2/15/22 4:40 AM, Roberto Sassu wrote:
> > ima_file_hash() has been modified to calculate the measurement of a file on
> > demand, if it has not been already performed by IMA. For compatibility
> > reasons, ima_inode_hash() remains unchanged.
> >
> > Keep the same approach in eBPF and introduce the new helper
> > bpf_ima_file_hash() to take advantage of the modified behavior of
> > ima_file_hash().
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> > ---
> >   include/uapi/linux/bpf.h       | 11 +++++++++++
> >   kernel/bpf/bpf_lsm.c           | 20 ++++++++++++++++++++
> >   tools/include/uapi/linux/bpf.h | 11 +++++++++++
> >   3 files changed, 42 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index b0383d371b9a..ba33d5718d6b 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -4648,6 +4648,16 @@ union bpf_attr {
> >    *		**-EOPNOTSUP** if IMA is disabled or **-EINVAL** if
> >    *		invalid arguments are passed.
> >    *
> > + * long bpf_ima_file_hash(struct file *file, void *dst, u32 size)
> > + *	Description
> > + *		Returns a calculated IMA hash of the *file*.
> > + *		If the hash is larger than *size*, then only *size*
> > + *		bytes will be copied to *dst*
> > + *	Return
> > + *		The **hash_algo** is returned on success,
> > + *		**-EOPNOTSUP** if the hash calculation failed or **-EINVAL**
> if
> > + *		invalid arguments are passed.
> > + *
> >    * struct socket *bpf_sock_from_file(struct file *file)
> >    *	Description
> >    *		If the given file represents a socket, returns the associated
> > @@ -5182,6 +5192,7 @@ union bpf_attr {
> >   	FN(bprm_opts_set),		\
> >   	FN(ktime_get_coarse_ns),	\
> >   	FN(ima_inode_hash),		\
> > +	FN(ima_file_hash),		\
> 
> Please put the above FN(ima_file_hash) to the end of the list.
> Otherwise, we have a backward compatability issue.

Hi Yonghong

sure, will do.

Thanks

Roberto

HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
Managing Director: Li Peng, Zhong Ronghua

> >   	FN(sock_from_file),		\
> >   	FN(check_mtu),			\
> >   	FN(for_each_map_elem),		\
> > diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
> > index 9e4ecc990647..e8d27af5bbcc 100644
> > --- a/kernel/bpf/bpf_lsm.c
> > +++ b/kernel/bpf/bpf_lsm.c
> [...]