From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f44.google.com (mail-pj1-f44.google.com [209.85.216.44]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 804103EFD0C for ; Fri, 5 Jun 2026 14:58:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.44 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780671490; cv=none; b=l/hF6rjuaLJYgMeJU4H+OFiM1Dla/dACP81tIivxble6sOtFbFG9pUDGJSerGu1DipSd4UEvxHONxtu2XRXI1ftwLjLwyZGxYzQLYUrkm6d8F1XOQVSR98EL+/rvuCPoaAo0n3QiGUrfh1/wRLHTWk/1ZwkRfVgOE8nuhTLMt8M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780671490; c=relaxed/simple; bh=r1iZ8a8iXyFQ7e9Yk84WkiexC6WpGev9TRhdGflQeHk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZNiKpmwOgV0RUkMQW/QDRg5Vf+AH+iGQLWueKq6pH8UVGeZDQThvUYUP1N0SROQL9q4YXBtviY7gv0D7tpuGc/vwFS9ejjD46INr23pPMz8STVEaVF1K5gpxrWAXjbnN61dIY/0Q3Vu4nWmKHzE/txuKzPQKtc8TtnEgJRHr6hQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=HTNNqYmZ; arc=none smtp.client-ip=209.85.216.44 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="HTNNqYmZ" Received: by mail-pj1-f44.google.com with SMTP id 98e67ed59e1d1-36b8e1760ccso1298335a91.0 for ; Fri, 05 Jun 2026 07:58:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1780671489; x=1781276289; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=QBALkfms9XINseZbRMjuo3U/MLkG0sUOcIH6JBjP30w=; b=HTNNqYmZLRAoLk4iXYiwjSK8k5m8Fs6u9WeisDtypgFcvCNmHFBNuKz9LHLgrwCSDd eSWj5N+TcSEIjmWVBHza98mFMus+nIG187pk+sqzFfwhMjzfwyhjgIw/h9wpH2Yv9bua FfV99zXXvuqWw9Gj3pA5XocaGKqGXYGSEt/a+QOYn8qbMMHmmFctiawaRFGj+DmpAvyT cMMeAN0sAg0xqMIhDSvLiXbGksmT1mJi/9yw7TvpO/HxY+MirMo2rF8kc03beKDBZZNZ +y9ETDTEvle1xbftVHduSvO9A5AFrl/Eq0tccqP1gCtcBbjKvVeXCyrGGAswO6Rn4kv2 QK+g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780671489; x=1781276289; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=QBALkfms9XINseZbRMjuo3U/MLkG0sUOcIH6JBjP30w=; b=V0Umw4R0FttKSxnJoobhP802ZPV3csEqmuQmeZsfmnWD3eBRTPLAfzeg6PxROY+zpd cz6t2Imrm38sIoCpfJpVyZSWhJHPfpHgYYPYiw6cpZQGbRj1vcMogoYSLbsowRh4mIp6 Zrj6k/2FGiPldGe5Xl+bTsNGmKXFjWvPG1WEQdExNYl1XybR9NVQ106I1qQfZDtqxacC 3nidykYO0RXFB2zch8zZ2UeA4IIdmpLMav71IXx0HHfNSLUt3m4XpISiSi81hZLd/Kb8 L8BUlMsglC1/33UCM2+QZQ7L5ppqmRtn5hV0yw/+/l1SRk3q8C+9lEhLx2mlU/vGiqi/ S1mg== X-Forwarded-Encrypted: i=1; AFNElJ9ZIZ6fR5QY/SX9yzVnP+Bruo7YPFXgVd2TW9FPRowHkxLFMUWxgAy1VDl0tDedCBG+BeyCqsdreyX5SJ8=@vger.kernel.org X-Gm-Message-State: AOJu0YwUb5v4ko+qqN65i03deQuRqj52NitFPNgNR01bi+L1Q6y8yzgJ ubm+3wQ2oaot92yzeolypn/56KA4o8Shy8GAelit1neAQ5ShOZ+QDA0i X-Gm-Gg: Acq92OESkk01oUX5UQwI++LPsrJF+ZT02OX6qlm0msSRpPfyFPwX+5ubc6mqipo5kEV QYkVrFeZTlt5/mgCIasgs98S9HFwPpU5DotIrflnJfSLtCDyTVPWu88juOBMkuhD9FYCXwdlrep /3yd6KhEUa/k43DTB2LM1j7dpe6iHHALHJ7mdaeMoDxilLLz0Lc4U/+C2MUcdedexYoKrD3M/az ucgxbxP84bXAPytkRbfjVZPKWxYAL1i5fNGFIKSpzyksHdvRuXahSPLTT70QLEvZ7q74iWVbxqT yub1EGmFH0JHe3jBxpWKB5XUAPDM7mJ//bzBrFKKbgRS9N60FLKv+7uzrJYJmQ5Xl+R4NM/QLRH h0AbuWqqoJQ8C9WzwtSeREdl6k2HoBPUsT5W/pEx95dmSvfhT1yFJjt4AOT2zPepAcsYoLsp7o4 nyWROgg9Zv5mqMWTIvNXP6fhglDSKxrM0jG3tifHFEX3opUFvzlJlJc8U6jnGfJlJN X-Received: by 2002:a17:90a:d643:b0:36b:b4a1:2939 with SMTP id 98e67ed59e1d1-370efda7ab1mr5078417a91.15.1780671488822; Fri, 05 Jun 2026 07:58:08 -0700 (PDT) Received: from m-upc-A520M-HDV.flets-east.jp ([2400:2410:3f60:500:1cda:ba68:a654:c3cf]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-36f70a28c0esm7058231a91.12.2026.06.05.07.58.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Jun 2026 07:58:08 -0700 (PDT) From: Yuyang Huang To: Yuyang Huang Cc: "David S. Miller" , David Ahern , Eric Dumazet , Ido Schimmel , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-kernel@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH net-next 1/2] ipv6: mcast: annotate data-races around mca_flags Date: Fri, 5 Jun 2026 23:57:58 +0900 Message-ID: <20260605145759.59639-2-sigefriedhyy@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260605145759.59639-1-sigefriedhyy@gmail.com> References: <20260605145759.59639-1-sigefriedhyy@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit /proc/net/igmp6 walks IPv6 multicast memberships under RCU and prints mca_flags without holding idev->mc_lock. The multicast paths update the field while holding idev->mc_lock. Annotate this intentional lockless snapshot with READ_ONCE() and the matching writers with WRITE_ONCE(). Signed-off-by: Yuyang Huang --- net/ipv6/mcast.c | 52 +++++++++++++++++++++++++++++------------------- 1 file changed, 32 insertions(+), 20 deletions(-) diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c index b8901c921c5e..bd3972730aa0 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -676,7 +676,7 @@ static void igmp6_group_added(struct ifmcaddr6 *mc) return; if (!(mc->mca_flags&MAF_LOADED)) { - mc->mca_flags |= MAF_LOADED; + WRITE_ONCE(mc->mca_flags, mc->mca_flags | MAF_LOADED); if (ndisc_mc_map(&mc->mca_addr, buf, dev, 0) == 0) dev_mc_add(dev, buf); } @@ -712,7 +712,7 @@ static void igmp6_group_dropped(struct ifmcaddr6 *mc) return; if (mc->mca_flags&MAF_LOADED) { - mc->mca_flags &= ~MAF_LOADED; + WRITE_ONCE(mc->mca_flags, mc->mca_flags & ~MAF_LOADED); if (ndisc_mc_map(&mc->mca_addr, buf, dev, 0) == 0) dev_mc_del(dev, buf); } @@ -886,7 +886,7 @@ static struct ifmcaddr6 *mca_alloc(struct inet6_dev *idev, if (ipv6_addr_is_ll_all_nodes(&mc->mca_addr) || IPV6_ADDR_MC_SCOPE(&mc->mca_addr) < IPV6_ADDR_SCOPE_LINKLOCAL) - mc->mca_flags |= MAF_NOREPORT; + WRITE_ONCE(mc->mca_flags, mc->mca_flags | MAF_NOREPORT); return mc; } @@ -1167,7 +1167,7 @@ static void igmp6_group_queried(struct ifmcaddr6 *ma, unsigned long resptime) if (!mod_delayed_work(mld_wq, &ma->mca_work, delay)) refcount_inc(&ma->mca_refcnt); - ma->mca_flags |= MAF_TIMER_RUNNING; + WRITE_ONCE(ma->mca_flags, ma->mca_flags | MAF_TIMER_RUNNING); } /* mark EXCLUDE-mode sources */ @@ -1195,7 +1195,7 @@ static bool mld_xmarksources(struct ifmcaddr6 *pmc, int nsrcs, } } } - pmc->mca_flags &= ~MAF_GSQUERY; + WRITE_ONCE(pmc->mca_flags, pmc->mca_flags & ~MAF_GSQUERY); if (scount == nsrcs) /* all sources excluded */ return false; return true; @@ -1227,10 +1227,10 @@ static bool mld_marksources(struct ifmcaddr6 *pmc, int nsrcs, } } if (!scount) { - pmc->mca_flags &= ~MAF_GSQUERY; + WRITE_ONCE(pmc->mca_flags, pmc->mca_flags & ~MAF_GSQUERY); return false; } - pmc->mca_flags |= MAF_GSQUERY; + WRITE_ONCE(pmc->mca_flags, pmc->mca_flags | MAF_GSQUERY); return true; } @@ -1499,18 +1499,25 @@ static void __mld_query_work(struct sk_buff *skb) } } else { for_each_mc_mclock(idev, ma) { + unsigned int flags; + if (!ipv6_addr_equal(&group, &ma->mca_addr)) continue; - if (ma->mca_flags & MAF_TIMER_RUNNING) { + flags = ma->mca_flags; + + if (flags & MAF_TIMER_RUNNING) { /* gsquery <- gsquery && mark */ if (!mark) - ma->mca_flags &= ~MAF_GSQUERY; + WRITE_ONCE(ma->mca_flags, + flags & ~MAF_GSQUERY); } else { /* gsquery <- mark */ if (mark) - ma->mca_flags |= MAF_GSQUERY; + WRITE_ONCE(ma->mca_flags, + flags | MAF_GSQUERY); else - ma->mca_flags &= ~MAF_GSQUERY; + WRITE_ONCE(ma->mca_flags, + flags & ~MAF_GSQUERY); } if (!(ma->mca_flags & MAF_GSQUERY) || mld_marksources(ma, ntohs(mlh2->mld2q_nsrcs), mlh2->mld2q_srcs)) @@ -1618,8 +1625,9 @@ static void __mld_report_work(struct sk_buff *skb) if (ipv6_addr_equal(&ma->mca_addr, &mld->mld_mca)) { if (cancel_delayed_work(&ma->mca_work)) refcount_dec(&ma->mca_refcnt); - ma->mca_flags &= ~(MAF_LAST_REPORTER | - MAF_TIMER_RUNNING); + WRITE_ONCE(ma->mca_flags, + ma->mca_flags & ~(MAF_LAST_REPORTER | + MAF_TIMER_RUNNING)); break; } } @@ -2018,8 +2026,10 @@ static struct sk_buff *add_grec(struct sk_buff *skb, struct ifmcaddr6 *pmc, if (pgr) pgr->grec_nsrcs = htons(scount); - if (isquery) - pmc->mca_flags &= ~MAF_GSQUERY; /* clear query state */ + if (isquery) { + /* clear query state */ + WRITE_ONCE(pmc->mca_flags, pmc->mca_flags & ~MAF_GSQUERY); + } return skb; } @@ -2612,7 +2622,8 @@ static void igmp6_join_group(struct ifmcaddr6 *ma) if (!mod_delayed_work(mld_wq, &ma->mca_work, delay)) refcount_inc(&ma->mca_refcnt); - ma->mca_flags |= MAF_TIMER_RUNNING | MAF_LAST_REPORTER; + WRITE_ONCE(ma->mca_flags, ma->mca_flags | + MAF_TIMER_RUNNING | MAF_LAST_REPORTER); } static int ip6_mc_leave_src(struct sock *sk, struct ipv6_mc_socklist *iml, @@ -2713,8 +2724,8 @@ static void mld_mca_work(struct work_struct *work) igmp6_send(&ma->mca_addr, ma->idev->dev, ICMPV6_MGM_REPORT); else mld_send_report(ma->idev, ma); - ma->mca_flags |= MAF_LAST_REPORTER; - ma->mca_flags &= ~MAF_TIMER_RUNNING; + WRITE_ONCE(ma->mca_flags, (ma->mca_flags | MAF_LAST_REPORTER) & + ~MAF_TIMER_RUNNING); mutex_unlock(&ma->idev->mc_lock); ma_put(ma); @@ -2972,13 +2983,14 @@ static int igmp6_mc_seq_show(struct seq_file *seq, void *v) { struct ifmcaddr6 *im = (struct ifmcaddr6 *)v; struct igmp6_mc_iter_state *state = igmp6_mc_seq_private(seq); + unsigned int mca_flags = READ_ONCE(im->mca_flags); seq_printf(seq, "%-4d %-15s %pi6 %5d %08X %ld\n", state->dev->ifindex, state->dev->name, &im->mca_addr, - READ_ONCE(im->mca_users), im->mca_flags, - (im->mca_flags & MAF_TIMER_RUNNING) ? + READ_ONCE(im->mca_users), mca_flags, + (mca_flags & MAF_TIMER_RUNNING) ? jiffies_to_clock_t(im->mca_work.timer.expires - jiffies) : 0); return 0; } -- 2.43.0