linux-kernel - Re: [PATCH v4 1/3] bpf/verifier: allow calling bpf_kptr

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Message-ID: <CAADnVQ+R-A1G7JO874fASUQNvDYuTeWovyvriCPth40Y=oLc9w@mail.gmail.com>
Date: Mon, 2 Feb 2026 17:18:10 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Chengkaitao <pilgrimtao@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	John Fastabend <john.fastabend@...il.com>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, 
	Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Shuah Khan <shuah@...nel.org>, Feng Yang <yangfeng@...inos.cn>, 
	LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>, Chengkaitao <chengkaitao@...inos.cn>
Subject: Re: [PATCH v4 1/3] bpf/verifier: allow calling bpf_kptr_xchg while
 holding a lock

On Mon, Feb 2, 2026 at 5:14 PM Chengkaitao <pilgrimtao@...il.com> wrote:
>
> On Tue, Feb 3, 2026 at 1:57 AM Alexei Starovoitov
> <alexei.starovoitov@...il.com> wrote:
> >
> > On Mon, Feb 2, 2026 at 1:01 AM Chengkaitao <pilgrimtao@...il.com> wrote:
> > >
> > > From: Chengkaitao <chengkaitao@...inos.cn>
> > >
> > > For the following scenario:
> > > struct tree_node {
> > >     struct bpf_rb_node node;
> > >     struct request __kptr *req;
> > >     u64 key;
> > > };
> > > struct bpf_rb_root tree_root __contains(tree_node, node);
> > > struct bpf_spin_lock tree_lock;
> > >
> > > If we need to traverse all nodes in the rbtree, retrieve the __kptr
> > > pointer from each node, and read kernel data from the referenced
> > > object, using bpf_kptr_xchg appears unavoidable.
> > >
> > > This patch skips the BPF verifier checks for bpf_kptr_xchg when
> > > called while holding a lock.
> > >
> > > Signed-off-by: Chengkaitao <chengkaitao@...inos.cn>
> >
> > You ignored earlier feedback. This is not ok.
> >
> It's my full name. Every region has its own customs and traditions,
> so this isn't an essential change.

We cannot accept your patch then.
SOB has to be "Firstname Lastname"