From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@meta.com>
Cc: Teng Qi <starmiku1207184332@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
John Fastabend <john.fastabend@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
bpf <bpf@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>
Subject: Re: [bug] kernel: bpf: syscall: a possible sleep-in-atomic bug in __bpf_prog_put()
Date: Wed, 24 May 2023 12:44:16 -0700 [thread overview]
Message-ID: <CAADnVQ+5GXu8Q1_awiHExhBB9_LmGrcPTvjQEjQU58pzX3WbQQ@mail.gmail.com> (raw)
In-Reply-To: <113dc8c1-0840-9ee3-2840-28246731604c@meta.com>
On Wed, May 24, 2023 at 12:34 PM Yonghong Song <yhs@meta.com> wrote:
>
>
>
> On 5/24/23 5:42 AM, Teng Qi wrote:
> > Thank you.
> >
> >> We cannot use rcu_read_lock_held() in the 'if' statement. The return
> >> value rcu_read_lock_held() could be 1 for some configurations regardless
> >> whether rcu_read_lock() is really held or not. In most cases,
> >> rcu_read_lock_held() is used in issuing potential warnings.
> >> Maybe there are other ways to record whether rcu_read_lock() is held or not?
> >
> > Sorry. I was not aware of the dependency of configurations of
> > rcu_read_lock_held().
> >
> >> If we cannot resolve rcu_read_lock() presence issue, maybe the condition
> >> can be !in_interrupt(), so any process-context will go to a workqueue.
> >
> > I agree that using !in_interrupt() as a condition is an acceptable solution.
>
> This should work although it could be conservative.
>
> >
> >> Alternatively, we could have another solution. We could add another
> >> function e.g., bpf_prog_put_rcu(), which indicates that bpf_prog_put()
> >> will be done in rcu context.
> >
> > Implementing a new function like bpf_prog_put_rcu() is a solution that involves
> > more significant changes.
>
> Maybe we can change signature of bpf_prog_put instead? Like
> void bpf_prog_put(struct bpf_prog *prog, bool in_rcu)
> and inside bpf_prog_put we can add
> WARN_ON_ONCE(in_rcu && !bpf_rcu_lock_held());
bpf_rcu_lock_held() is used for different cases.
Here s/in_irq/in_interrupt/ inside bpf_prog_put() is enough
to address this theoretical issue.
next prev parent reply other threads:[~2023-05-24 19:44 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-16 11:18 [bug] kernel: bpf: syscall: a possible sleep-in-atomic bug in __bpf_prog_put() starmiku1207184332
2023-05-16 17:08 ` Yonghong Song
[not found] ` <CALyQVax8X63qekZVhvRTmZFFs+ucPKRkBB7UnRZk6Hu3ggi7Og@mail.gmail.com>
2023-05-21 3:44 ` Yonghong Song
[not found] ` <CALyQVazb=D1ejapiFdTnan6JbjFJA2q9ifhSsmF4OC9MDz3oAw@mail.gmail.com>
2023-05-23 4:33 ` Yonghong Song
2023-05-24 12:42 ` Teng Qi
2023-05-24 19:34 ` Yonghong Song
2023-05-24 19:44 ` Alexei Starovoitov [this message]
2023-05-25 5:37 ` Yonghong Song
2023-06-11 13:02 ` Teng Qi
2023-06-12 0:01 ` Yonghong Song
2023-06-19 9:05 ` Teng Qi
2023-06-19 19:01 ` Yonghong Song
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