[bpf-next,v2,4/7] bpf/verifier: add ARG_PTR_TO_UNINIT_MAP_VALUE

ARG_PTR_TO_UNINIT_MAP_VALUE argument is a pointer to a memory zone
used to save the value of a map.  Basically the same as
ARG_PTR_TO_UNINIT_MEM, but the size has not be passed as an extra
argument.

This will be used in the following patch that implements some new
helpers that receive a pointer to be filled with a map value.

Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>
---
 include/linux/bpf.h   |    1 +
 kernel/bpf/verifier.c |    9 ++++++---
 2 files changed, 7 insertions(+), 3 deletions(-)

On Wed, Oct 10, 2018 at 7:06 AM Mauricio Vasquez B
<mauricio.vasquez@polito.it> wrote:
>
> ARG_PTR_TO_UNINIT_MAP_VALUE argument is a pointer to a memory zone
> used to save the value of a map.  Basically the same as
> ARG_PTR_TO_UNINIT_MEM, but the size has not be passed as an extra
> argument.
>
> This will be used in the following patch that implements some new
> helpers that receive a pointer to be filled with a map value.
>
> Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>
Acked-by: Song Liu <songliubraving@fb.com>
> ---
>  include/linux/bpf.h   |    1 +
>  kernel/bpf/verifier.c |    9 ++++++---
>  2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 5793f0c7fbb5..e37b4986bb45 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -139,6 +139,7 @@ enum bpf_arg_type {
>         ARG_CONST_MAP_PTR,      /* const argument used as pointer to bpf_map */
>         ARG_PTR_TO_MAP_KEY,     /* pointer to stack used as map key */
>         ARG_PTR_TO_MAP_VALUE,   /* pointer to stack used as map value */
> +       ARG_PTR_TO_UNINIT_MAP_VALUE,    /* pointer to valid memory used to store a map value */
>
>         /* the following constraints used to prototype bpf_memcmp() and other
>          * functions that access data on eBPF program stack
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 3f93a548a642..d84c91ac3b70 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -2117,7 +2117,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
>         }
>
>         if (arg_type == ARG_PTR_TO_MAP_KEY ||
> -           arg_type == ARG_PTR_TO_MAP_VALUE) {
> +           arg_type == ARG_PTR_TO_MAP_VALUE ||
> +           arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
>                 expected_type = PTR_TO_STACK;
>                 if (!type_is_pkt_pointer(type) && type != PTR_TO_MAP_VALUE &&
>                     type != expected_type)
> @@ -2187,7 +2188,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
>                 err = check_helper_mem_access(env, regno,
>                                               meta->map_ptr->key_size, false,
>                                               NULL);
> -       } else if (arg_type == ARG_PTR_TO_MAP_VALUE) {
> +       } else if (arg_type == ARG_PTR_TO_MAP_VALUE ||
> +                  arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
>                 /* bpf_map_xxx(..., map_ptr, ..., value) call:
>                  * check [value, value + map->value_size) validity
>                  */
> @@ -2196,9 +2198,10 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno,
>                         verbose(env, "invalid map_ptr to access map->value\n");
>                         return -EACCES;
>                 }
> +               meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE);
>                 err = check_helper_mem_access(env, regno,
>                                               meta->map_ptr->value_size, false,
> -                                             NULL);
> +                                             meta);
>         } else if (arg_type_is_mem_size(arg_type)) {
>                 bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);
>
>