From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 90B45256C70; Fri, 23 Jan 2026 21:43:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769204586; cv=none; b=fm3fm9wvdQiBdLj+INyDvbuWJOzgTyH34ippxwISBJu/hkQ+7Pjlzw+uosOZgtV2mwJ3X9D2/J34Jhb9TcGYGpb7/n9tJoEbFbkiwOmqD4UPpZd+p2JBwVfe3Cgv/sbnCsCJhoAbv5wOSAn/Mjv82U1OzAwTgjoPMM02y1tsUtI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769204586; c=relaxed/simple; bh=KheEDbybRqccT4YssL9LzHDPm7tF5WT0v2sGWl6zBxc=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=J5fdSTSz0v7X933xsHgDTar9b1A6Tff6+woIdYhsIUMaX81vs7xeaT95Ye2/MzBWRMBQebBAsMRk6VALzA6vtB93/8FJh7n9hbK828cUXwu1CenKif42pTgPubv1llT94v+/Ysyd2J1dTpEtpSpfDGsVjhlbcdhtPwEyRjaMjDI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rssnGl86; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="rssnGl86" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 40B97C4CEF1; Fri, 23 Jan 2026 21:43:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769204586; bh=KheEDbybRqccT4YssL9LzHDPm7tF5WT0v2sGWl6zBxc=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=rssnGl86RvKZD83WgWSS3e0Qm1GV6iygavQHn/9Lo5jH+ybnZLtqajqv+yL/r/znc iBaMgd5BRYnPqObJld6zlIzf1UtmSJm9mJhlIYivwBCQEAujrskPSLJvoAHgU00EZL NH+y/P3/xP8DkfEPgCL2AxfvM/NKc/+tLI4DaLdWIapISGPduyckL64TWL1wGgRg48 AI6BVZkuMxH3cosb24CVfbQHBo26UN7KVsMCR7LAIh1IH1uWsAHCxPIRn9Q0txy9Vn rM4bvbySyTKOuJBgsbTrE5NtVaVJk4F5p5n2WL89vxAMTTQMmzrmwak1UsaQPDC0Oc sNcxOOYcJResg== Date: Fri, 23 Jan 2026 13:43:05 -0800 (PST) From: Mat Martineau To: Eric Dumazet cc: "David S . Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , Matthieu Baerts , Geliang Tang , Florian Westphal , netdev@vger.kernel.org, mptcp@lists.linux.dev, eric.dumazet@gmail.com, syzbot+5498a510ff9de39d37da@syzkaller.appspotmail.com, Eulgyu Kim , Geliang Tang Subject: Re: [PATCH v2 net] mptcp: fix race in mptcp_pm_nl_flush_addrs_doit() In-Reply-To: <20260123030327.3041148-1-edumazet@google.com> Message-ID: <36367d05-e05f-c86b-7125-e98b529f9d0c@kernel.org> References: <20260123030327.3041148-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed On Fri, 23 Jan 2026, Eric Dumazet wrote: > syzbot and Eulgyu Kim reported crashes in mptcp_pm_nl_get_local_id() > and/or mptcp_pm_nl_is_backup() > > Root cause is list_splice_init() in mptcp_pm_nl_flush_addrs_doit() > which is not RCU ready. > > list_splice_init_rcu() can not be called here while holding pernet->lock > spinlock. > > Many thanks to Eulgyu Kim for providing a repro and testing our patches. > > Fixes: 141694df6573 ("mptcp: remove address when netlink flushes addrs") > Signed-off-by: Eric Dumazet > Reported-by: syzbot+5498a510ff9de39d37da@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/all/6970a46d.a00a0220.3ad28e.5cf0.GAE@google.com/T/ > Reported-by: Eulgyu Kim > Cc: Geliang Tang > --- > v2: Make sure the list was not empty, return early otherwise. Thanks Eric, the v2 code changes LGTM. The netdev tooling wasn't able to apply the patch (https://patchwork.kernel.org/project/netdevbpf/patch/20260123030327.3041148-1-edumazet@google.com/), so Matthieu is planning to send a basically-identical v3 that 'git am' and the netdev CI will be happy with. Reviewed-by: Mat Martineau > v1: https://lore.kernel.org/netdev/20260122131306.2119853-1-edumazet@google.com/ > > net/mptcp/pm_kernel.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c > index 57570a44e4185370f531047fe97ce9f9fbd1480b..af23be6658ded4860133bb9495c7738014815d28 100644 > --- a/net/mptcp/pm_kernel.c > +++ b/net/mptcp/pm_kernel.c > @@ -1294,16 +1294,28 @@ static void __reset_counters(struct pm_nl_pernet *pernet) > int mptcp_pm_nl_flush_addrs_doit(struct sk_buff *skb, struct genl_info *info) > { > struct pm_nl_pernet *pernet = genl_info_pm_nl(info); > - LIST_HEAD(free_list); > + struct list_head free_list; > > spin_lock_bh(&pernet->lock); > - list_splice_init(&pernet->endp_list, &free_list); > + > + free_list = pernet->endp_list; > + INIT_LIST_HEAD_RCU(&pernet->endp_list); > + > __reset_counters(pernet); > pernet->next_id = 1; > bitmap_zero(pernet->id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1); > spin_unlock_bh(&pernet->lock); > - mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list); > + > + if (free_list.next == &pernet->endp_list) > + return 0; > + > synchronize_rcu(); > + > + /* Adjust the pointers to free_list instead of pernet->endp_list */ > + free_list.prev->next = &free_list; > + free_list.next->prev = &free_list; > + > + mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list); > __flush_addrs(&free_list); > return 0; > } > -- > 2.52.0.457.g6b5491de43-goog > >