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Fri, 05 Jun 2026 19:45:53 -0700 (PDT) Received: from tux ([2601:7c0:c37e:2360:d412:6d5d:4bc3:48b2]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-660d6488b1csm6493022d50.19.2026.06.05.19.45.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Jun 2026 19:45:52 -0700 (PDT) From: Ethan Tidmore To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Amery Hung , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Cc: John Fastabend , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Ethan Tidmore Subject: [PATCH] bpf: Fix signedness bug Date: Fri, 5 Jun 2026 21:45:40 -0500 Message-ID: <20260606024540.47362-1-ethantidmore06@gmail.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The function acquire_reference() returns negative error codes and 'id' is an unsigned integer, so the check (id < 0) is always impossible. Detected by Smatch: kernel/bpf/verifier.c:13115 check_kfunc_call() warn: unsigned 'id' is never less than zero. Fixes: 308c7a0ae8859 ("bpf: Refactor object relationship tracking and fix d= ynptr UAF bug") Signed-off-by: Ethan Tidmore --- kernel/bpf/verifier.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8ed484cb1a8a..aa8f10fce071 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -13111,9 +13111,11 @@ static int check_kfunc_call(struct bpf_verifier_en= v *env, struct bpf_insn *insn, } mark_btf_func_reg_size(env, BPF_REG_0, sizeof(void *)); if (is_kfunc_acquire(&meta)) { - id =3D acquire_reference(env, insn_idx, 0); - if (id < 0) - return id; + err =3D acquire_reference(env, insn_idx, 0); + if (err < 0) + return err; + id =3D err; + regs[BPF_REG_0].id =3D id; } else if (is_rbtree_node_type(ptr_type) || is_list_node_type(ptr_type))= { ref_set_non_owning(env, ®s[BPF_REG_0]); --=20 Thanks, ET https://github.com/sponsors/ethantidmore