Re: [v2 PATCH bpf-next 1/2] bpf: Check percpu map value size first

[Andrii Nakryiko]

On Mon, Sep 9, 2024 at 12:14 AM Tao Chen <chen.dylane@xxxxxxxxx> wrote:
>
> Percpu map is often used, but the map value size limit often ignored,
> like issue: https://github.com/iovisor/bcc/issues/2519. Actually,
> percpu map value size is bound by PCPU_MIN_UNIT_SIZE, so we
> can check the value size whether it exceeds PCPU_MIN_UNIT_SIZE first,
> like percpu map of local_storage. Maybe the error message seems clearer
> compared with "cannot allocate memory".
>
> Signed-off-by: Tao Chen <chen.dylane@xxxxxxxxx>
> Signed-off-by: jinke han <jinkehan@xxxxxxxxxxxxxx>

names in SOB should be capitalized

the check is useful, so:

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>

> ---
>  kernel/bpf/arraymap.c | 3 +++
>  kernel/bpf/hashtab.c  | 3 +++
>  2 files changed, 6 insertions(+)
>
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index a43e62e2a8bb..79660e3fca4c 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -73,6 +73,9 @@ int array_map_alloc_check(union bpf_attr *attr)
>         /* avoid overflow on round_up(map->value_size) */
>         if (attr->value_size > INT_MAX)
>                 return -E2BIG;
> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
> +               return -E2BIG;
>
>         return 0;
>  }
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 45c7195b65ba..b14b87463ee0 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -462,6 +462,9 @@ static int htab_map_alloc_check(union bpf_attr *attr)
>                  * kmalloc-able later in htab_map_update_elem()
>                  */
>                 return -E2BIG;
> +       /* percpu map value size is bound by PCPU_MIN_UNIT_SIZE */
> +       if (percpu && round_up(attr->value_size, 8) > PCPU_MIN_UNIT_SIZE)
> +               return -E2BIG;
>
>         return 0;
>  }
> --
> 2.25.1
>