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Sat, 15 Aug 2026 11:00:52 -0700 (PDT) Message-ID: <668871823f90f69896d3db27b56db2f53e481162.camel@gmail.com> Subject: Re: [PATCH bpf-next v5 11/14] bpf: Report Call Type Safety argument errors From: Eduard Zingerman To: bot+bpf-ci@kernel.org, memxor@gmail.com, bpf@vger.kernel.org Cc: ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, emil@etsalapatis.com, kkd@meta.com, kernel-team@meta.com, martin.lau@kernel.org, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Date: Sat, 15 Aug 2026 11:00:48 -0700 In-Reply-To: <3eda33675965763aa9b2e6a5784f32b34a6a83988a55fbea98b0dbd0cf3b088d@mail.kernel.org> References: <20260815064612.378577-12-memxor@gmail.com> <3eda33675965763aa9b2e6a5784f32b34a6a83988a55fbea98b0dbd0cf3b088d@mail.kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-10 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sat, 2026-08-15 at 07:49 +0000, bot+bpf-ci@kernel.org wrote: > > diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c > > index 5d20ea9e470e..99784d465881 100644 > > --- a/kernel/bpf/diagnostics.c > > +++ b/kernel/bpf/diagnostics.c >=20 > [ ... ] >=20 > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index f5bf8cf644b8..2c067be53106 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c >=20 > [ ... ] >=20 > > @@ -12417,29 +12552,43 @@ static int check_kfunc_args(struct bpf_verifi= er_env *env, struct bpf_call_arg_me > >=20 > > =C2=A0 t =3D btf_type_skip_modifiers(btf, args[i].type, NULL); > >=20 > > - if (btf_type_is_ptr(t) && (bpf_register_is_null(reg) || type_may_be_n= ull(reg->type)) && > > + if (btf_type_is_ptr(t)) { > > + ref_t =3D btf_type_skip_modifiers(btf, t->type, &ref_id); > > + ref_tname =3D btf_name_by_offset(btf, ref_t->name_off); > > + } > > + > > + if (btf_type_is_ptr(t) && > > + =C2=A0=C2=A0=C2=A0 (bpf_register_is_null(reg) || type_may_be_null(reg= ->type)) && > > =C2=A0 =C2=A0=C2=A0=C2=A0 !type_may_be_null(kf_arg_type)) { > > + const char *expected_type; > > + > > + expected_type =3D bpf_diag_fmt_btf_type(env, btf, ref_id); > > =C2=A0 verbose(env, "Possibly NULL pointer passed to trusted %s\n", > > =C2=A0 reg_arg_name(env, argno)); > > + bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name, > > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "Add a NULL check and call the kfun= c only on the non-NULL path.", > > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "the pointer may be NULL, but this = kfunc requires a non-NULL pointer to %s", > > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 expected_type); > > =C2=A0 return -EACCES; > > =C2=A0 } > >=20 > > =C2=A0 if (regno =3D=3D meta->release_regno && !is_kfunc_arg_dynptr(met= a->btf, &args[i]) && > > =C2=A0 =C2=A0=C2=A0=C2=A0 !reg_is_referenced(env, reg) && !bpf_register= _is_null(reg)) { > > + const char *expected_type; > > + > > + expected_type =3D bpf_diag_fmt_btf_type(env, btf, ref_id); > > =C2=A0 verbose(env, "release kfunc %s expects referenced PTR_TO_BTF_ID= passed to %s\n", > > =C2=A0 func_name, reg_arg_name(env, argno)); > > + bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name, > > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "Pass the resource-owning pointer r= eturned by the matching acquire kfunc, and avoid calling the release kfunc = after ownership has already been transferred or released.", > > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 "release kfuncs require a resource-= owning value of type %s returned by a matching acquire kfunc", > > + =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 expected_type); > > =C2=A0 return -EINVAL; > > =C2=A0 } >=20 > When the kfunc parameter is a plain void*, will bpf_diag_fmt_btf_type() > format it correctly? For a void* parameter, ref_id becomes 0 after > btf_type_skip_modifiers() and bpf_diag_fmt_btf_type() produces the > literal string "()" for type ID 0. This is legit btf.c:btf_show_name() needs a fix: --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -1172,9 +1172,9 @@ static const char *btf_show_name(struct btf_show *s= how) id =3D 0; break; } + t =3D btf_type_skip_qualifiers(show->btf, id); if (!id) break; - t =3D btf_type_skip_qualifiers(show->btf, id); } /* We may not be able to represent this type; bail to be safe */ if (i =3D=3D BTF_SHOW_MAX_ITER) ...