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Message-ID: <CAADnVQLsqV2q3Ury+p3_6n4eph+TWAVRFSVWst803k6XV_qf6g@mail.gmail.com>
Date: Mon, 22 Jul 2024 17:58:04 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: Juntong Deng <juntong.deng@...look.com>, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, John Fastabend <john.fastabend@...il.com>,
Martin KaFai Lau <martin.lau@...ux.dev>, Eddy Z <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>,
Andrii Nakryiko <andrii@...nel.org>, Andrei Vagin <avagin@...il.com>, snorcht@...il.com,
bpf <bpf@...r.kernel.org>, Network Development <netdev@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH bpf-next RESEND 00/16] bpf: Checkpoint/Restore In eBPF (CRIB)
On Mon, Jul 22, 2024 at 5:50 PM Kumar Kartikeya Dwivedi
<memxor@...il.com> wrote:
>
> >
> > > Currently we cannot pass the pointer returned by the iterator next
> > > method as argument to the KF_TRUSTED_ARGS kfuncs, because the pointer
> > > returned by the iterator next method is not "valid".
>
> I've replied to this particular patch to explain what exact unsafety
> it might introduce.
What do you mean?
I think we can make the return value from iter_next() trusted in
certain cases.
For example bpf_iter_task_next() returns task_struct and it
can be safely marked as MEM_RCU, since the whole iterator is
KF_RCU_PROTECTED.
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