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SubjectRe: [PATCH v2 3/6] bpf-lsm: Introduce new helper bpf_ima_file_hash()
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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@huawei.com>
> ---
> 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.

> 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
[...]

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