Re: [PATCH RFC v3 bpf-next 2/4] bpf: Add bpf_copy_from_user() helper.

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Thu, Jun 11, 2020 at 3:24 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> From: Alexei Starovoitov <ast@kernel.org>
>
> Sleepable BPF programs can now use copy_from_user() to access user memory.
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>  include/linux/bpf.h            |  1 +
>  include/uapi/linux/bpf.h       | 11 ++++++++++-
>  kernel/bpf/helpers.c           | 22 ++++++++++++++++++++++
>  kernel/trace/bpf_trace.c       |  2 ++
>  tools/include/uapi/linux/bpf.h | 11 ++++++++++-
>  5 files changed, 45 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 6819000682a5..c8c9217f3ac9 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1632,6 +1632,7 @@ extern const struct bpf_func_proto bpf_ringbuf_reserve_proto;
>  extern const struct bpf_func_proto bpf_ringbuf_submit_proto;
>  extern const struct bpf_func_proto bpf_ringbuf_discard_proto;
>  extern const struct bpf_func_proto bpf_ringbuf_query_proto;
> +extern const struct bpf_func_proto bpf_copy_from_user_proto;
>
>  const struct bpf_func_proto *bpf_tracing_func_proto(
>         enum bpf_func_id func_id, const struct bpf_prog *prog);
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 0bef454c9598..a38c806d34ad 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3260,6 +3260,13 @@ union bpf_attr {
>   *             case of **BPF_CSUM_LEVEL_QUERY**, the current skb->csum_level
>   *             is returned or the error code -EACCES in case the skb is not
>   *             subject to CHECKSUM_UNNECESSARY.
> + *
> + * int bpf_copy_from_user(void *dst, u32 size, const void *user_ptr)

Can we also add bpf_copy_str_from_user (or bpf_copy_from_user_str,
whichever makes more sense) as well?

> + *     Description
> + *             Read *size* bytes from user space address *user_ptr* and store
> + *             the data in *dst*. This is a wrapper of copy_from_user().
> + *     Return
> + *             0 on success, or a negative error in case of failure.
>   */

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