From: Eduard Zingerman <eddyz87@gmail.com>
To: bot+bpf-ci@kernel.org, kaitao.cheng@linux.dev, ast@kernel.org,
corbet@lwn.net, martin.lau@linux.dev, daniel@iogearbox.net,
andrii@kernel.org, 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
Cc: bpf@vger.kernel.org, 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
Subject: Re: [PATCH RESEND bpf-next v10 2/8] bpf: clear list node owner and unlink before drop
Date: Wed, 13 May 2026 15:53:59 -0700 [thread overview]
Message-ID: <e141699dab70282d811ec30bbf2aa8279706817b.camel@gmail.com> (raw)
In-Reply-To: <da95f45b43d94d17796b19abc4c555e35daafab7d5e1cdca3714fe0f54ab8cce@mail.kernel.org>
On Tue, 2026-05-12 at 06:41 +0000, bot+bpf-ci@kernel.org wrote:
[...]
> When a BPF program holds an owning or refcount-acquired reference to
> one of these nodes (node X), which is structurally supported because
> __bpf_obj_drop_impl() uses refcount_dec_and_test() and only frees at
> refcount 0, a concurrent push to a DIFFERENT bpf_list_head becomes a
> corruption:
>
> CPU 0 (bpf_list_head_free, lock released) CPU 1 (BPF prog, refcount X)
> ----------------------------------------- ----------------------------
> (owner of X == NULL, X linked in drain)
> bpf_list_push_back(other, X)
> __bpf_list_add: spin_lock()
> cmpxchg(X->owner, NULL,
> POISON) -> OK
> list_add_tail(&X->list_head,
> other_head)
> -> overwrites X->next,
> X->prev, corrupts
> other_head's chain
> because X is still
> stitched into drain
> pos = drain.next; (may be X or neighbor using X's stale next)
> list_del_init(pos); reads X->next/prev now pointing into other_head,
> corrupts other_head's list and/or drain
Kaitao, this scenario seem plausible, could you please comment on it?
[...]
next prev parent reply other threads:[~2026-05-13 22:54 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 5:59 [PATCH RESEND bpf-next v10 0/8] bpf: Extend the bpf_list family of APIs Kaitao cheng
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 1/8] bpf: refactor __bpf_list_del to take list node pointer Kaitao cheng
2026-05-12 6:41 ` bot+bpf-ci
2026-05-12 8:55 ` Kaitao Cheng
2026-05-13 22:30 ` Eduard Zingerman
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 2/8] bpf: clear list node owner and unlink before drop Kaitao cheng
2026-05-12 6:41 ` bot+bpf-ci
2026-05-13 22:53 ` Eduard Zingerman [this message]
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 3/8] bpf: Introduce the bpf_list_del kfunc Kaitao cheng
2026-05-12 6:41 ` bot+bpf-ci
2026-05-12 9:36 ` Kaitao Cheng
2026-05-13 22:32 ` Eduard Zingerman
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 4/8] bpf: refactor __bpf_list_add to take insertion point via **prev_ptr Kaitao cheng
2026-05-13 22:33 ` Eduard Zingerman
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 5/8] bpf: Add bpf_list_add to insert node after a given list node Kaitao cheng
2026-05-12 6:41 ` bot+bpf-ci
2026-05-12 12:05 ` Kaitao Cheng
2026-05-13 22:35 ` Eduard Zingerman
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 6/8] bpf: add bpf_list_is_first/last/empty kfuncs Kaitao cheng
2026-05-13 22:35 ` Eduard Zingerman
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 7/8] bpf: allow non-owning list-node args via __nonown_allowed Kaitao cheng
2026-05-12 6:41 ` bot+bpf-ci
2026-05-13 22:37 ` Eduard Zingerman
2026-05-13 22:55 ` Eduard Zingerman
2026-05-12 5:59 ` [PATCH RESEND bpf-next v10 8/8] selftests/bpf: Add test cases for bpf_list_del/add/is_first/is_last/empty Kaitao cheng
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