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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dr9o/D4m; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dr9o/D4m" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B82551F00A3A; Mon, 7 Sep 2026 13:55:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788789337; bh=jJ+ndCZNHT0zDxYtMGHvipLR4TlMKPnMFQNGeNYe0UQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=dr9o/D4m5aWfOMIZIuItB2ZIbjE6/Fbh7NdnM4RTMVVBNqxzGtzrADh0ftgSM1EFj AQhQ+f+SZveyvFTt1bZ/lDwfEl/gqlmeHbiOE3sAir7iuhotdaNXOXJD6PkT6/ROXl WxWKRAQf3IYvveeyXMp5N13ROiAUZXvX3W0yatl7lnRJeqR0+5cfbViPZw2ggSgutN dyL1HT9Zd1aIyQNea3AL+a3lLjzjBaQD4+VQGYshflf4TMoCHu6YJ6Mf+7kA1y4VFA 2HYJz6ZO79KGctQK76uJJUKGqg6ZW2hBftPTixNQ/eYJT4xk2QPklVVTBE6jcVnTAR 2mkJcizj3sBag== Message-ID: Date: Mon, 7 Sep 2026 15:55:34 +0200 Precedence: bulk X-Mailing-List: mptcp@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Beta Subject: Re: [PATCH mptcp-net v3 1/3] mptcp: fix data-race in __mptcp_retrans / mptcp_incoming_options Content-Language: fr To: Paolo Abeni Cc: Geliang Tang , quanyeyang@proton.me, MPTCP Linux References: <20260907-mptcp-snd-una-race-v3-0-65ba0d5f0221@proton.me> <20260907-mptcp-snd-una-race-v3-1-65ba0d5f0221@proton.me> <87fb99e7-df73-46b8-97a1-4d6173121ab5@redhat.com> From: Matthieu Baerts Autocrypt: addr=matttbe@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Paolo, On 07/09/2026 15:38, Paolo Abeni wrote: > On 9/7/26 12:15 PM, quanyeyang@proton.me wrote: >> From: "Matthieu Baerts (NGI0)" >> >> SyzKaller found this data-race: >> >> BUG: KCSAN: data-race in __mptcp_retrans / mptcp_incoming_options >> >> write (marked) to 0xffff888015e8e5f0 of 8 bytes by interrupt on cpu 0: >> __mptcp_snd_una_update net/mptcp/options.c:1055 [inline] >> mptcp_incoming_options+0x6a3/0x1ac0 net/mptcp/options.c:1183 >> tcp_data_queue+0x101b/0x2440 net/ipv4/tcp_input.c:5583 >> tcp_rcv_established+0x684/0x1fc0 net/ipv4/tcp_input.c:6654 >> tcp_v4_do_rcv+0x35c/0x690 net/ipv4/tcp_ipv4.c:1866 >> tcp_v4_rcv+0x1d91/0x25a0 net/ipv4/tcp_ipv4.c:2263 >> ip_protocol_deliver_rcu+0x46/0x280 net/ipv4/ip_input.c:207 >> ip_local_deliver_finish+0x190/0x270 net/ipv4/ip_input.c:241 >> NF_HOOK include/linux/netfilter.h:318 [inline] >> NF_HOOK include/linux/netfilter.h:312 [inline] >> ip_local_deliver+0xe3/0x210 net/ipv4/ip_input.c:262 >> dst_input include/net/dst.h:480 [inline] >> ip_rcv_finish net/ipv4/ip_input.c:492 [inline] >> NF_HOOK include/linux/netfilter.h:318 [inline] >> NF_HOOK include/linux/netfilter.h:312 [inline] >> ip_rcv+0x200/0x220 net/ipv4/ip_input.c:612 >> __netif_receive_skb_one_core+0xeb/0x110 net/core/dev.c:6178 >> __netif_receive_skb+0x1f/0xc0 net/core/dev.c:6291 >> process_backlog+0x168/0x360 net/core/dev.c:6642 >> __napi_poll+0x71/0x460 net/core/dev.c:7706 >> napi_poll net/core/dev.c:7769 [inline] >> net_rx_action+0x6f8/0x810 net/core/dev.c:7926 >> handle_softirqs+0xc9/0x2e0 kernel/softirq.c:622 >> run_ksoftirqd kernel/softirq.c:1063 [inline] >> run_ksoftirqd+0x20/0x30 kernel/softirq.c:1055 >> smpboot_thread_fn+0x287/0x520 kernel/smpboot.c:160 >> kthread+0x1f2/0x240 kernel/kthread.c:436 >> ret_from_fork+0x321/0x440 arch/x86/kernel/process.c:158 >> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 >> >> read to 0xffff888015e8e5f0 of 8 bytes by task 24 on cpu 1: >> mptcp_rtx_head net/mptcp/protocol.h:487 [inline] >> __mptcp_retrans+0x169/0x8f0 net/mptcp/protocol.c:2759 >> mptcp_worker+0x6a6/0xb30 net/mptcp/protocol.c:2980 >> process_one_work+0x3ee/0x970 kernel/workqueue.c:3275 >> process_scheduled_works kernel/workqueue.c:3358 [inline] >> worker_thread+0x3c3/0x730 kernel/workqueue.c:3439 >> kthread+0x1f2/0x240 kernel/kthread.c:436 >> ret_from_fork+0x321/0x440 arch/x86/kernel/process.c:158 >> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 > > I think this race is not present in the current tree, after commit > 96d846e3e2a7 ("mptcp: let the retrans scheduler do its job"). Thank you for having checked. Good point, this old patch is maybe outdated, I didn't check. Note that on syzkaller side, the last occurrence I had for this issue was on the 13th of May, and your patch was in on tree on the 3rd of June. I guess it is indeed not needed then. (I don't know why I didn't see it after the 13th of May, but there were no reproducers.) Cheers, Matt -- Sponsored by the NGI0 Core fund.