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Sat, 14 Feb 2026 04:41:13 -0800 (PST) Received: from localhost.localdomain ([113.218.252.61]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-824c6a2e40bsm7064497b3a.11.2026.02.14.04.41.08 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 14 Feb 2026 04:41:12 -0800 (PST) From: Chengkaitao To: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, yangfeng@kylinos.cn, alexei.starovoitov@gmail.com Cc: linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Kaitao Cheng Subject: [PATCH RESEND v7 4/5] bpf: allow using bpf_kptr_xchg even if the MEM_RCU flag is set Date: Sat, 14 Feb 2026 20:40:41 +0800 Message-ID: <20260214124042.62229-5-pilgrimtao@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260214124042.62229-1-pilgrimtao@gmail.com> References: <20260214124042.62229-1-pilgrimtao@gmail.com> 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" From: Kaitao Cheng For the following scenario: struct tree_node { struct bpf_refcount ref; struct bpf_rb_node node; struct node_data __kptr * node_data; u64 key; }; This means node_data would have the type PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU. When traversing an rbtree using bpf_rbtree_left/right, if we need to use bpf_kptr_xchg to read the __kptr pointer, we still need to follow the remove-read-add sequence. This patch allows us to use bpf_kptr_xchg to directly read the __kptr pointer without any prior operations. Signed-off-by: Kaitao Cheng Signed-off-by: Feng Yang --- kernel/bpf/verifier.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3536a91ff8c7..f673cdb55961 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -9331,6 +9331,7 @@ static const struct bpf_reg_types kptr_xchg_dest_type= s =3D { PTR_TO_MAP_VALUE, PTR_TO_BTF_ID | MEM_ALLOC, PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF, + PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU, } }; static const struct bpf_reg_types dynptr_types =3D { @@ -9491,6 +9492,7 @@ static int check_reg_type(struct bpf_verifier_env *en= v, u32 regno, case PTR_TO_BTF_ID | MEM_ALLOC: case PTR_TO_BTF_ID | MEM_PERCPU | MEM_ALLOC: case PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF: + case PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF | MEM_RCU: if (meta->func_id !=3D BPF_FUNC_spin_lock && meta->func_id !=3D BPF_FUNC= _spin_unlock && meta->func_id !=3D BPF_FUNC_kptr_xchg) { verifier_bug(env, "unimplemented handling of MEM_ALLOC"); --=20 2.50.1 (Apple Git-155)