linux-kernel - Re: [PATCH] bpf: extend btf id list

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Date:   Fri, 7 Apr 2023 10:34:45 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Tom Rix <trix@...hat.com>
Cc:     martin.lau@...ux.dev, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, song@...nel.org, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, nathan@...nel.org,
        joannelkoong@...il.com, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] bpf: extend btf id list

On Tue, Mar 7, 2023 at 7:13 AM Tom Rix <trix@...hat.com> wrote:
>
> With clang and W=1, there is this error
>
> kernel/bpf/verifier.c:10298:24: error: array index 16 is past
>  the end of the array (that has type 'u32[16]'
>  (aka 'unsigned int[16]')) [-Werror,-Warray-bounds]
>     meta.func_id == special_kfunc_list[KF_bpf_dynptr_slice_rdwr]) {
>                     ^                  ~~~~~~~~~~~~~~~~~~~~~~~~
> kernel/bpf/verifier.c:9150:1: note: array 'special_kfunc_list' declared here
> BTF_ID_LIST(special_kfunc_list)
> ^
> ./include/linux/btf_ids.h:207:27: note: expanded from macro 'BTF_ID_LIST'
>  #define BTF_ID_LIST(name) static u32 __maybe_unused name[16];
>
> When KF_bpf_dynptr_slice_rdwr was added to the enum special_kfunc_type
> the total exceeded 16.  Increase the array size to 32.
>
> Fixes: 66e3a13e7c2c ("bpf: Add bpf_dynptr_slice and bpf_dynptr_slice_rdwr")

Looks like Nathan's patch got picked up.
commit 2d5bcdcda879 ("bpf: Increase size of BTF_ID_LIST without
CONFIG_DEBUG_INFO_BTF again")
https://lore.kernel.org/bpf/20230307-bpf-kfuncs-warray-bounds-v1-1-00ad3191f3a6@kernel.org/

> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  include/linux/btf_ids.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
> index 3a4f7cd882ca..166c387b48f7 100644
> --- a/include/linux/btf_ids.h
> +++ b/include/linux/btf_ids.h
> @@ -204,7 +204,7 @@ extern struct btf_id_set8 name;
>
>  #else
>
> -#define BTF_ID_LIST(name) static u32 __maybe_unused name[16];
> +#define BTF_ID_LIST(name) static u32 __maybe_unused name[32];
>  #define BTF_ID(prefix, name)
>  #define BTF_ID_FLAGS(prefix, name, ...)
>  #define BTF_ID_UNUSED
> --
> 2.27.0
>
>


-- 
Thanks,
~Nick Desaulniers