Re: [PATCH bpf-next 01/11] bpf: Add a bpf keyring for program signature validation

> diff --git a/include/linux/verification.h b/include/linux/verification.h
> index dec7f2beabfd4..1cb59ddda2509 100644
> --- a/include/linux/verification.h
> +++ b/include/linux/verification.h
> @@ -18,6 +18,16 @@
>  #define VERIFY_USE_SECONDARY_KEYRING ((struct key *)1UL)
>  #define VERIFY_USE_PLATFORM_KEYRING  ((struct key *)2UL)
>
> +/*
> + * The id of BPF's ".bpf" keyring, reserved from the same space. It is
> + * explicitly not a sentinel like the two above as BPF resolves it to
> + * the keyring itself and passes that, so verify_pkcs7_signature() never
> + * sees this value, and system_keyring_id_check() must keep rejecting it.
> + * Left as a plain integer so that handing it over as @trusted_keys does
> + * not compile.

Does the comment accurately describe what the code enforces?

The comment states the value is "left as a plain integer so that handing
it over as @trusted_keys does not compile." Passing the integer 3 where
struct key *trusted_keys is expected triggers -Wint-conversion, but that
warning is not promoted to -Werror anywhere in scripts/Makefile.warn or
scripts/Makefile.extrawarn.

The kernel requires -Werror=implicit-function-declaration,
-Werror=implicit-int, -Werror=return-type, -Werror=strict-prototypes, and
-Werror=incompatible-pointer-types, but -Werror=int-conversion appears
nowhere. int-conversion only became a hard error by compiler default in
GCC 14 and Clang 16, while Documentation/process/changes.rst still lists
GCC 8.1 as the minimum supported version.

On a GCC 8.1-13 build, the misuse compiles with only a warning rather than
an error. Could the phrasing be adjusted to reflect that this is a warning
rather than a guaranteed compile-time failure across the full supported
toolchain range?

> + */
> +#define VERIFY_USE_BPF_KEYRING	3
> +
>  static inline int system_keyring_id_check(u64 id)
>  {
>  	if (id > (unsigned long)VERIFY_USE_PLATFORM_KEYRING)


---
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See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/32530917987