Re: [PATCH bpf-next v1 03/13] bpf: Rename confusingly named RET_PTR_TO_ALLOC_MEM

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On Tue, Oct 18, 2022 at 6:59 AM Kumar Kartikeya Dwivedi
<memxor@xxxxxxxxx> wrote:
>
> Currently, the verifier has two return types, RET_PTR_TO_ALLOC_MEM, and
> RET_PTR_TO_ALLOC_MEM_OR_NULL, however the former is confusingly named to
> imply that it carries MEM_ALLOC, while only the latter does. This causes
> confusion during code review leading to conclusions like that the return
> value of RET_PTR_TO_DYNPTR_MEM_OR_NULL (which is RET_PTR_TO_ALLOC_MEM |
> PTR_MAYBE_NULL) may be consumable by bpf_ringbuf_{submit,commit}.
>
> Rename it to make it clear MEM_ALLOC needs to be tacked on top of
> RET_PTR_TO_MEM.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
>  include/linux/bpf.h   | 6 +++---
>  kernel/bpf/verifier.c | 2 +-
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 13c6ff2de540..834276ba56c9 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -538,7 +538,7 @@ enum bpf_return_type {
>         RET_PTR_TO_SOCKET,              /* returns a pointer to a socket */
>         RET_PTR_TO_TCP_SOCK,            /* returns a pointer to a tcp_sock */
>         RET_PTR_TO_SOCK_COMMON,         /* returns a pointer to a sock_common */
> -       RET_PTR_TO_ALLOC_MEM,           /* returns a pointer to dynamically allocated memory */
> +       RET_PTR_TO_MEM,                 /* returns a pointer to dynamically allocated memory */
>         RET_PTR_TO_MEM_OR_BTF_ID,       /* returns a pointer to a valid memory or a btf_id */
>         RET_PTR_TO_BTF_ID,              /* returns a pointer to a btf_id */
>         __BPF_RET_TYPE_MAX,
> @@ -548,8 +548,8 @@ enum bpf_return_type {
>         RET_PTR_TO_SOCKET_OR_NULL       = PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
>         RET_PTR_TO_TCP_SOCK_OR_NULL     = PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
>         RET_PTR_TO_SOCK_COMMON_OR_NULL  = PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
> -       RET_PTR_TO_ALLOC_MEM_OR_NULL    = PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM,
> -       RET_PTR_TO_DYNPTR_MEM_OR_NULL   = PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
> +       RET_PTR_TO_ALLOC_MEM_OR_NULL    = PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_MEM,

Can you also rename this to RET_PTR_TO_RINGBUF_MEM_OR_NULL instead of
RET_PTR_TO_ALLOC_MEM_OR_NULL, and MEM_RINGBUF instead of MEM_ALLOC?
RET_PTR_TO_ALLOC_MEM_OR_NULL only pertains to ringbuf records, not
generic dynamically allocated memory, so I think this rename would
make this a lot more clear.

> +       RET_PTR_TO_DYNPTR_MEM_OR_NULL   = PTR_MAYBE_NULL | RET_PTR_TO_MEM,
>         RET_PTR_TO_BTF_ID_OR_NULL       = PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
>
>         /* This must be the last entry. Its purpose is to ensure the enum is
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 87d9cccd1623..a49b95c1af1b 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -7612,7 +7612,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
>                 mark_reg_known_zero(env, regs, BPF_REG_0);
>                 regs[BPF_REG_0].type = PTR_TO_TCP_SOCK | ret_flag;
>                 break;
> -       case RET_PTR_TO_ALLOC_MEM:
> +       case RET_PTR_TO_MEM:
>                 mark_reg_known_zero(env, regs, BPF_REG_0);
>                 regs[BPF_REG_0].type = PTR_TO_MEM | ret_flag;
>                 regs[BPF_REG_0].mem_size = meta.mem_size;
> --
> 2.38.0
>



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