From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-176.mta1.migadu.com (out-176.mta1.migadu.com [95.215.58.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 666F93CB2FD for ; Tue, 12 May 2026 12:06:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778587591; cv=none; b=et3qmUM/AdNHzMK7TxSaaypqCjihAXqfMapVxzdPQkMWE7FGIggZW8BIGdiii+cwN1jayTRs8TxU8wBo6MnxmQ9hSLjsuXQNXpMicsJLtYMl9x+KQQUT1HX5i0e2uy0BUMekBbTViHveL87bRPMzukHGoz2Ztn0AtN5Axphh/d4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778587591; c=relaxed/simple; bh=p/tHk3Ki7ukILe77/bmVvcIMX8dUCZhWCuNG0mGDJjY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Osornl3prkLc57nR8ig3zU/nhK1OOD7/r5QdyhUOsPFkt3zGlTk/8XozrmnKVlbaOfmWX4/cgxC3O1vwUOI3+SGguwYMrwb3BAlDtgudWqSDkkCwWi6eRIw1o0XlC+E3fw4GETG31thVgfnwaouYxLVZxfNbU/VSVUX83YZrv4A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=I+M8YmPX; arc=none smtp.client-ip=95.215.58.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="I+M8YmPX" Message-ID: <1e3e5461-76cb-4e69-81f8-fb2220bf797c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1778587577; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Ap2nfY1WZm6T5NE1j7FvcA+Rbuv0o1NHLF2th8iyNUI=; b=I+M8YmPXQjQDW/l4DymajI9lHONPQvH/p43t4tlzHtFeU9DBE5bi0PJBgeo3tVXpo2Xvwz 3PvQKsUX01TNh9+d6MawmNdT2f+P83j3QgbFOsKIOYLE3UH3kJ3SmlKEc6ZLXeWhtIK7rv 2F6A2S2YBrcbnM8zP8J+n8o0Nlm0z58= Date: Tue, 12 May 2026 20:05:15 +0800 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH RESEND bpf-next v10 5/8] bpf: Add bpf_list_add to insert node after a given list node To: bot+bpf-ci@kernel.org Cc: bpf@vger.kernel.org, ast@kernel.org, corbet@lwn.net, martin.lau@linux.dev, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, shuah@kernel.org, chengkaitao@kylinos.cn, skhan@linuxfoundation.org, memxor@gmail.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, vmalik@redhat.com, linux-kselftest@vger.kernel.org, martin.lau@kernel.org, clm@meta.com, ihor.solodrai@linux.dev References: <20260512055919.95716-6-kaitao.cheng@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Kaitao Cheng In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 在 2026/5/12 14:41, bot+bpf-ci@kernel.org 写道: >> diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c >> --- a/kernel/bpf/helpers.c >> +++ b/kernel/bpf/helpers.c >> @@ -2570,6 +2570,16 @@ __bpf_kfunc int bpf_list_push_back_impl(struct bpf_list_head *head, >> return bpf_list_push_back(head, node, meta__ign, off); >> } >> >> +__bpf_kfunc int bpf_list_add(struct bpf_list_head *head, struct bpf_list_node *new, >> + struct bpf_list_node *prev, struct btf_struct_meta *meta, >> + u64 off) > > The commit message states that 'prev' must already be in the list. How can a > BPF program obtain such a reference and pass it to this kfunc? > > A node already in the list is tracked by the verifier as a non-owning > reference (PTR_TO_BTF_ID | MEM_ALLOC | NON_OWN_REF with ref_obj_id == 0). > The typical way to obtain this is via bpf_list_front() or bpf_list_back(), > which return non-owning references. > > However, check_kfunc_args() in kernel/bpf/verifier.c handles > KF_ARG_PTR_TO_LIST_NODE by requiring owning references and rejects non-owning > references. > > Without a similar distinction for KF_ARG_PTR_TO_LIST_NODE (as exists for > KF_ARG_PTR_TO_RB_NODE), is there any valid BPF register state that satisfies > both the verifier check and the runtime semantics stated in the commit > message? > > The BPF CI bot reported this issue in v10. The author responded that this was > fixed in [PATCH bpf-next v10 7/8], which introduces the __nonown_allowed > annotation and corresponding verifier logic. However, patch 7/8 is not > present in this commit (feed006fb969), so the parameter lacks the > __nonown_allowed suffix and the verifier lacks the is_kfunc_arg_nonown_allowed() > check. If this is an issue that must be fixed, I will move [PATCH bpf-next v10 7/8] earlier in the next version. > Reference: https://lore.kernel.org/bpf/cb7368c6062232b6ad5f9ab1c6a97bc8530566a8b3db5c4deefdd5ea63d31538@mail.kernel.org/ > >> +{ >> + struct bpf_list_node_kern *n = (void *)new, *p = (void *)prev; >> + struct list_head *prev_ptr = &p->list_head; >> + >> + return __bpf_list_add(n, head, &prev_ptr, meta ? meta->record : NULL, off); >> +} >> + > > [ ... ] > >> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >> --- a/kernel/bpf/verifier.c >> +++ b/kernel/bpf/verifier.c > > [ ... ] > >> @@ -19235,8 +19238,11 @@ struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) }; >> int struct_meta_reg = BPF_REG_3; >> int node_offset_reg = BPF_REG_4; >> >> - /* rbtree_add has extra 'less' arg, so args-to-fixup are in diff regs */ >> - if (is_bpf_rbtree_add_kfunc(desc->func_id)) { >> + /* list_add/rbtree_add have an extra arg (prev/less), >> + * so args-to-fixup are in diff regs. >> + */ > > This isn't a bug, but the multi-line comment format doesn't follow the BPF > subsystem style. The preferred form in kernel/bpf/ has the opening /* on its > own line: > > /* > * list_add/rbtree_add have an extra arg (prev/less), > * so args-to-fixup are in diff regs. > */ > >> + if (desc->func_id == special_kfunc_list[KF_bpf_list_add] || >> + is_bpf_rbtree_add_kfunc(desc->func_id)) { >> struct_meta_reg = BPF_REG_4; >> node_offset_reg = BPF_REG_5; >> } > > > --- > AI reviewed your patch. Please fix the bug or email reply why it's not a bug. > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md > > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/25716874656 -- Thanks Kaitao Cheng