From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: xxx@vger.kernel.org, jiayuan.chen@shopee.com,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Stanislav Fomichev <sdf@fomichev.me>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
KP Singh <kpsingh@kernel.org>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Clark Williams <clrkwllms@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@kernel.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev
Subject: Re: [PATCH bpf v3 2/2] bpf: devmap: fix race in bq_xmit_all on PREEMPT_RT
Date: Tue, 17 Feb 2026 08:42:12 +0100 [thread overview]
Message-ID: <20260217074212.95wNTgR7@linutronix.de> (raw)
In-Reply-To: <20260213034018.284146-3-jiayuan.chen@linux.dev>
On 2026-02-13 11:40:15 [+0800], Jiayuan Chen wrote:
…
> timeslicing during the mdelay window causes interleaving. Without the
> fix, KASAN reports null-ptr-deref due to operating on freed frames:
>
> BUG: KASAN: null-ptr-deref in __build_skb_around+0x22d/0x340
> Write of size 32 at addr 0000000000000d50 by task devmap_race_rep/449
>
> CPU: 0 UID: 0 PID: 449 Comm: devmap_race_rep Not tainted 6.19.0+ #31 PREEMPT_RT
> Call Trace:
> <TASK>
> __build_skb_around+0x22d/0x340
> build_skb_around+0x25/0x260
> __xdp_build_skb_from_frame+0x103/0x860
> veth_xdp_rcv_bulk_skb.isra.0+0x162/0x320
> veth_xdp_rcv.constprop.0+0x61e/0xbb0
> veth_poll+0x280/0xb50
> __napi_poll.constprop.0+0xa5/0x590
> net_rx_action+0x4b0/0xea0
> handle_softirqs.isra.0+0x1b3/0x780
> __local_bh_enable_ip+0x12a/0x240
> xdp_test_run_batch.constprop.0+0xedd/0x1f60
> bpf_test_run_xdp_live+0x304/0x640
> bpf_prog_test_run_xdp+0xd24/0x1b70
> __sys_bpf+0x61c/0x3e00
> </TASK>
>
> Kernel panic - not syncing: Fatal exception in interrupt
I would move this next to the diffstat (same as with the previous
patch) since it is obvious once you described it.
Sebastian
next prev parent reply other threads:[~2026-02-17 7:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-13 3:40 [PATCH bpf v3 0/2] bpf: cpumap/devmap: fix per-CPU bulk queue races on PREEMPT_RT Jiayuan Chen
2026-02-13 3:40 ` [PATCH bpf v3 1/2] bpf: cpumap: fix race in bq_flush_to_queue " Jiayuan Chen
2026-02-13 3:40 ` [PATCH bpf v3 2/2] bpf: devmap: fix race in bq_xmit_all " Jiayuan Chen
2026-02-17 7:42 ` Sebastian Andrzej Siewior [this message]
2026-02-17 7:43 ` [PATCH bpf v3 0/2] bpf: cpumap/devmap: fix per-CPU bulk queue races " Sebastian Andrzej Siewior
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