[RFC,bpf-next,v1,1/8] bpf: add a get_helper_proto() utility function

Commit Message

Eduard Zingerman June 29, 2024, 9:47 a.m. UTC

Extract the part of check_helper_call() as a utility function allowing
to query 'struct bpf_func_proto' for a specific helper function id.

Signed-off-by: Eduard Zingerman <[e-mail]>
---
 kernel/bpf/verifier.c | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

Comments

Andrii Nakryiko July 2, 2024, 12:41 a.m. UTC | #1

On Sat, Jun 29, 2024 at 2:48 AM Eduard Zingerman <[e-mail]> wrote:
>
> Extract the part of check_helper_call() as a utility function allowing
> to query 'struct bpf_func_proto' for a specific helper function id.
>
> Signed-off-by: Eduard Zingerman <[e-mail]>
> ---
>  kernel/bpf/verifier.c | 37 ++++++++++++++++++++++++++-----------
>  1 file changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index d3927d819465..8dd3385cf925 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -10261,6 +10261,24 @@ static void update_loop_inline_state(struct bpf_verifier_env *env, u32 subprogno
>                                  state->callback_subprogno == subprogno);
>  }
>
> +static int get_helper_proto(struct bpf_verifier_env *env, int func_id,
> +                           const struct bpf_func_proto **ptr)
> +{
> +       const struct bpf_func_proto *result = NULL;
> +
> +       if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID)
> +               return -ERANGE;
> +
> +       if (env->ops->get_func_proto)
> +               result = env->ops->get_func_proto(func_id, env->prog);
> +
> +       if (!result)
> +               return -EINVAL;
> +
> +       *ptr = result;
> +       return 0;
> +}
> +
>  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
>                              int *insn_idx_p)
>  {
> @@ -10277,17 +10295,14 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
>
>         /* find function prototype */
>         func_id = insn->imm;
> -       if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
> -               verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
> -                       func_id);
> -               return -EINVAL;
> -       }
> -
> -       if (env->ops->get_func_proto)
> -               fn = env->ops->get_func_proto(func_id, env->prog);
> -       if (!fn) {
> -               verbose(env, "program of this type cannot use helper %s#%d\n",
> -                       func_id_name(func_id), func_id);
> +       err = get_helper_proto(env, insn->imm, &fn);
> +       if (err) {
> +               if (err == -ERANGE)
> +                       verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
> +                               func_id);
> +               else
> +                       verbose(env, "program of this type cannot use helper %s#%d\n",
> +                               func_id_name(func_id), func_id);
>                 return -EINVAL;
>         }

subjective, but this might be cleaner and will keep first verbose() on
a single line:

err = get_helper_proto(...);
if (err == -ERANGE) {
    verbose(...);
    return -EINVAL;
} else if (err) {
    verbose(...);
    return err;
}


>
> --
> 2.45.2
>

Eduard Zingerman July 2, 2024, 8:07 p.m. UTC | #2

On Mon, 2024-07-01 at 17:41 -0700, Andrii Nakryiko wrote:

[...]

> subjective, but this might be cleaner and will keep first verbose() on
> a single line:
> 
> err = get_helper_proto(...);
> if (err == -ERANGE) {
>     verbose(...);
>     return -EINVAL;
> } else if (err) {
>     verbose(...);
>     return err;
> }

Will do.

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d3927d819465..8dd3385cf925 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -10261,6 +10261,24 @@  static void update_loop_inline_state(struct bpf_verifier_env *env, u32 subprogno
 				 state->callback_subprogno == subprogno);
 }
 
+static int get_helper_proto(struct bpf_verifier_env *env, int func_id,
+			    const struct bpf_func_proto **ptr)
+{
+	const struct bpf_func_proto *result = NULL;
+
+	if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID)
+		return -ERANGE;
+
+	if (env->ops->get_func_proto)
+		result = env->ops->get_func_proto(func_id, env->prog);
+
+	if (!result)
+		return -EINVAL;
+
+	*ptr = result;
+	return 0;
+}
+
 static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			     int *insn_idx_p)
 {
@@ -10277,17 +10295,14 @@  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 
 	/* find function prototype */
 	func_id = insn->imm;
-	if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
-		verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
-			func_id);
-		return -EINVAL;
-	}
-
-	if (env->ops->get_func_proto)
-		fn = env->ops->get_func_proto(func_id, env->prog);
-	if (!fn) {
-		verbose(env, "program of this type cannot use helper %s#%d\n",
-			func_id_name(func_id), func_id);
+	err = get_helper_proto(env, insn->imm, &fn);
+	if (err) {
+		if (err == -ERANGE)
+			verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
+				func_id);
+		else
+			verbose(env, "program of this type cannot use helper %s#%d\n",
+				func_id_name(func_id), func_id);
 		return -EINVAL;
 	}