On Mon, Jul 11, 2022 at 10:32:18AM +0200, Artem Savkov wrote:
> Add a BPF_F_DESTRUCTIVE will be required to be supplied to
> BPF_PROG_LOAD for programs to utilize destructive helpers such as
> bpf_panic().
I'd think that having kernel.destructive_bpf_enabled sysctl knob enabled
would be enough to enable that helper from any program, not sure having
extra load flag adds more security
jirka
>
> Signed-off-by: Artem Savkov <asavkov@xxxxxxxxxx>
> ---
> include/linux/bpf.h | 1 +
> include/uapi/linux/bpf.h | 6 ++++++
> kernel/bpf/syscall.c | 4 +++-
> tools/include/uapi/linux/bpf.h | 6 ++++++
> 4 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 77972724bed7..43c008e3587a 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1041,6 +1041,7 @@ struct bpf_prog_aux {
> bool sleepable;
> bool tail_call_reachable;
> bool xdp_has_frags;
> + bool destructive;
> bool use_bpf_prog_pack;
> /* BTF_KIND_FUNC_PROTO for valid attach_btf_id */
> const struct btf_type *attach_func_proto;
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index e81362891596..4423874b5da4 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -1121,6 +1121,12 @@ enum bpf_link_type {
> */
> #define BPF_F_XDP_HAS_FRAGS (1U << 5)
>
> +/* If BPF_F_DESTRUCTIVE is used in BPF_PROG_LOAD command, the loaded program
> + * will be able to perform destructive operations such as calling bpf_panic()
> + * helper.
> + */
> +#define BPF_F_DESTRUCTIVE (1U << 6)
> +
> /* link_create.kprobe_multi.flags used in LINK_CREATE command for
> * BPF_TRACE_KPROBE_MULTI attach type to create return probe.
> */
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 1ce6541d90e1..779feac2dc7d 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -2449,7 +2449,8 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
> BPF_F_TEST_STATE_FREQ |
> BPF_F_SLEEPABLE |
> BPF_F_TEST_RND_HI32 |
> - BPF_F_XDP_HAS_FRAGS))
> + BPF_F_XDP_HAS_FRAGS |
> + BPF_F_DESTRUCTIVE))
> return -EINVAL;
>
> if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
> @@ -2536,6 +2537,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr)
> prog->aux->offload_requested = !!attr->prog_ifindex;
> prog->aux->sleepable = attr->prog_flags & BPF_F_SLEEPABLE;
> prog->aux->xdp_has_frags = attr->prog_flags & BPF_F_XDP_HAS_FRAGS;
> + prog->aux->destructive = attr->prog_flags & BPF_F_DESTRUCTIVE;
>
> err = security_bpf_prog_alloc(prog->aux);
> if (err)
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index e81362891596..4423874b5da4 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -1121,6 +1121,12 @@ enum bpf_link_type {
> */
> #define BPF_F_XDP_HAS_FRAGS (1U << 5)
>
> +/* If BPF_F_DESTRUCTIVE is used in BPF_PROG_LOAD command, the loaded program
> + * will be able to perform destructive operations such as calling bpf_panic()
> + * helper.
> + */
> +#define BPF_F_DESTRUCTIVE (1U << 6)
> +
> /* link_create.kprobe_multi.flags used in LINK_CREATE command for
> * BPF_TRACE_KPROBE_MULTI attach type to create return probe.
> */
> --
> 2.35.3
>
