[PATCH bpf] bpf: Gate dynptr API behind CAP_BPF

[PATCH bpf] bpf: Gate dynptr API behind CAP_BPF

[Kumar Kartikeya Dwivedi]

This has been enabled for unprivileged programs for only one kernel
release, hence the expected annoyances due to this move are low. Users
using ringbuf can stick to non-dynptr APIs. The actual use cases dynptr
is meant to serve may not make sense in unprivileged BPF programs.

Hence, gate these helpers behind CAP_BPF and limit use to privileged
BPF programs.

Fixes: 263ae152e962 ("bpf: Add bpf_dynptr_from_mem for local dynptrs")
Fixes: bc34dee65a65 ("bpf: Dynptr support for ring buffers")
Fixes: 13bbbfbea759 ("bpf: Add bpf_dynptr_read and bpf_dynptr_write")
Fixes: 34d4ef5775f7 ("bpf: Add dynptr data slices")
Cc: stable@vger.kernel.org # v5.19+
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/helpers.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 41aeaf3862ec..f57a08b6dddb 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1607,26 +1607,12 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_ringbuf_discard_proto;
 	case BPF_FUNC_ringbuf_query:
 		return &bpf_ringbuf_query_proto;
-	case BPF_FUNC_ringbuf_reserve_dynptr:
-		return &bpf_ringbuf_reserve_dynptr_proto;
-	case BPF_FUNC_ringbuf_submit_dynptr:
-		return &bpf_ringbuf_submit_dynptr_proto;
-	case BPF_FUNC_ringbuf_discard_dynptr:
-		return &bpf_ringbuf_discard_dynptr_proto;
 	case BPF_FUNC_strncmp:
 		return &bpf_strncmp_proto;
 	case BPF_FUNC_strtol:
 		return &bpf_strtol_proto;
 	case BPF_FUNC_strtoul:
 		return &bpf_strtoul_proto;
-	case BPF_FUNC_dynptr_from_mem:
-		return &bpf_dynptr_from_mem_proto;
-	case BPF_FUNC_dynptr_read:
-		return &bpf_dynptr_read_proto;
-	case BPF_FUNC_dynptr_write:
-		return &bpf_dynptr_write_proto;
-	case BPF_FUNC_dynptr_data:
-		return &bpf_dynptr_data_proto;
 	default:
 		break;
 	}
@@ -1659,6 +1645,20 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_for_each_map_elem_proto;
 	case BPF_FUNC_loop:
 		return &bpf_loop_proto;
+	case BPF_FUNC_ringbuf_reserve_dynptr:
+		return &bpf_ringbuf_reserve_dynptr_proto;
+	case BPF_FUNC_ringbuf_submit_dynptr:
+		return &bpf_ringbuf_submit_dynptr_proto;
+	case BPF_FUNC_ringbuf_discard_dynptr:
+		return &bpf_ringbuf_discard_dynptr_proto;
+	case BPF_FUNC_dynptr_from_mem:
+		return &bpf_dynptr_from_mem_proto;
+	case BPF_FUNC_dynptr_read:
+		return &bpf_dynptr_read_proto;
+	case BPF_FUNC_dynptr_write:
+		return &bpf_dynptr_write_proto;
+	case BPF_FUNC_dynptr_data:
+		return &bpf_dynptr_data_proto;
 	default:
 		break;
 	}
--
2.34.1

Re: [PATCH bpf] bpf: Gate dynptr API behind CAP_BPF

[Andrii Nakryiko]

On Wed, Sep 21, 2022 at 1:27 AM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> This has been enabled for unprivileged programs for only one kernel
> release, hence the expected annoyances due to this move are low. Users
> using ringbuf can stick to non-dynptr APIs. The actual use cases dynptr
> is meant to serve may not make sense in unprivileged BPF programs.
>
> Hence, gate these helpers behind CAP_BPF and limit use to privileged
> BPF programs.
>
> Fixes: 263ae152e962 ("bpf: Add bpf_dynptr_from_mem for local dynptrs")
> Fixes: bc34dee65a65 ("bpf: Dynptr support for ring buffers")
> Fixes: 13bbbfbea759 ("bpf: Add bpf_dynptr_read and bpf_dynptr_write")
> Fixes: 34d4ef5775f7 ("bpf: Add dynptr data slices")
> Cc: stable@vger.kernel.org # v5.19+
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> ---

Acked-by: Andrii Nakryiko <andrii@kernel.org>

>  kernel/bpf/helpers.c | 28 ++++++++++++++--------------
>  1 file changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
> index 41aeaf3862ec..f57a08b6dddb 100644
> --- a/kernel/bpf/helpers.c
> +++ b/kernel/bpf/helpers.c
> @@ -1607,26 +1607,12 @@ bpf_base_func_proto(enum bpf_func_id func_id)
>                 return &bpf_ringbuf_discard_proto;
>         case BPF_FUNC_ringbuf_query:
>                 return &bpf_ringbuf_query_proto;
> -       case BPF_FUNC_ringbuf_reserve_dynptr:
> -               return &bpf_ringbuf_reserve_dynptr_proto;
> -       case BPF_FUNC_ringbuf_submit_dynptr:
> -               return &bpf_ringbuf_submit_dynptr_proto;
> -       case BPF_FUNC_ringbuf_discard_dynptr:
> -               return &bpf_ringbuf_discard_dynptr_proto;
>         case BPF_FUNC_strncmp:
>                 return &bpf_strncmp_proto;
>         case BPF_FUNC_strtol:
>                 return &bpf_strtol_proto;
>         case BPF_FUNC_strtoul:
>                 return &bpf_strtoul_proto;
> -       case BPF_FUNC_dynptr_from_mem:
> -               return &bpf_dynptr_from_mem_proto;
> -       case BPF_FUNC_dynptr_read:
> -               return &bpf_dynptr_read_proto;
> -       case BPF_FUNC_dynptr_write:
> -               return &bpf_dynptr_write_proto;
> -       case BPF_FUNC_dynptr_data:
> -               return &bpf_dynptr_data_proto;
>         default:
>                 break;
>         }
> @@ -1659,6 +1645,20 @@ bpf_base_func_proto(enum bpf_func_id func_id)
>                 return &bpf_for_each_map_elem_proto;
>         case BPF_FUNC_loop:
>                 return &bpf_loop_proto;
> +       case BPF_FUNC_ringbuf_reserve_dynptr:
> +               return &bpf_ringbuf_reserve_dynptr_proto;
> +       case BPF_FUNC_ringbuf_submit_dynptr:
> +               return &bpf_ringbuf_submit_dynptr_proto;
> +       case BPF_FUNC_ringbuf_discard_dynptr:
> +               return &bpf_ringbuf_discard_dynptr_proto;
> +       case BPF_FUNC_dynptr_from_mem:
> +               return &bpf_dynptr_from_mem_proto;
> +       case BPF_FUNC_dynptr_read:
> +               return &bpf_dynptr_read_proto;
> +       case BPF_FUNC_dynptr_write:
> +               return &bpf_dynptr_write_proto;
> +       case BPF_FUNC_dynptr_data:
> +               return &bpf_dynptr_data_proto;
>         default:
>                 break;
>         }
> --
> 2.34.1
>