From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) (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 1B63F3EC830 for ; Fri, 28 Aug 2026 08:45:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.197 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787906745; cv=none; b=kwJZcoIl+MFvDtIWuV4ETOZix64VLkYU/SvOufdX8wWhMVNdOD6ECTRFLVGD9+kmF0Vo+5uAk326pMhAjAcqaiDlOP9POz6oH7MoShX6olO4qWlcK/zsR9dp9jb6FbNESzof4z2zNVWoaHovYVyI0YiUMJYXRSCh1N/hz9ov30A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787906745; c=relaxed/simple; bh=wHZm5T6MXfIHf1aB3xeVf+l7MfOlOZRP+jCO3ynpwmM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=VK7nPoe2V4/p724l6XKv6AmUfNfAxVXUqKQeTWqcIhi+FdFfytEKIHUlw1bmQR4kWazb8W7D7a/g+pU00zUdldTquK1ZXOoMXjp/duqX9UMb91+oZpEjwEA5oKov8ZC7AB8sSxQPHiBoo9GyTjRf9JWJ9v+bn9xF+ha9fj590s0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=Fp/V6vYO; arc=none smtp.client-ip=209.85.222.197 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Fp/V6vYO" Received: by mail-qk1-f197.google.com with SMTP id af79cd13be357-9390ca1a9abso106412985a.2 for ; Fri, 28 Aug 2026 01:45:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787906742; x=1788511542; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=gmGTmfvPMul0lpOk9GNEl2916otB+JSQDPLwkYrikSc=; b=Fp/V6vYOLJeayAJhUkT/kMP5lRY8wnAZS9F4heK9wsUdYb1tv2T3MmDmZEukmLlaLJ J6La8xQy+0xMQ3rRb/x1zkR9+KDHMj8FuChlpmajAHZ8Nym0wznt9HVwIU6aDB9u9AzS 6Uc15lUpk154OBOO5pCYglrdvZBfg83txPwjyMjTjqdPl+S2fhmjt5qr77Lr3r99kcmx HIdYUr8Vya04UqQfxtL524rfzuDe5YoqWM2rwaLmlw20waGo8SjnNHXO2iprAknksQvz bDnD7VFvBIy5px08lCwiCYi4U+KJl1AVls3es/1oDkKAvijP/YdFFx+U6iGD/V4Jltpg Ps2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787906742; x=1788511542; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=gmGTmfvPMul0lpOk9GNEl2916otB+JSQDPLwkYrikSc=; b=PlDW3hru0TL+JERIkdhdxgkMsHmmWeYmlu1/pn8QKpU5jk8oh7xPD37Cbkpd/sM2qT fuJ7wj057DP+Er1pneyC/VEX4iuU6wSzISKSxpft26gpMNWYlqc5+Xurki5i6WTVSZxq vX0Vj7qj67eU26xAcobdk7bVOkK6I0XhLuMzX5Lx+j5Wf5JS45LupNtMh0uySQNGeLqj bQOQ3776Tq1aIYI3E82rt/7kR+o5KxiGTAfGoX9fdf9o7qYakLZkU/Z3T/Yi/9AT+FD6 BFwjSdgUUb/NYDBBQU0yC/otmzonO63INVp/ZfOiWPvPVeAO8A3QJWvUvC3k8FDiAyuz 79ww== X-Forwarded-Encrypted: i=1; AHgh+RpjY8669/6RFcT9XrzomFMMzH9mtgGLrqZtQfTQQ8q9tBDw80Ja0+V2G5LFcMS4Qg1r2FX/kRI=@vger.kernel.org X-Gm-Message-State: AFuF++k/XVpeeldcHiYt/UvH/OJMT+e1XWAhm34scHbMdLx+9r+GQE8j 5YerVKQvpzhnyOC2FHBtt/z2ZAE4Ynr+FYrrSH+t90D5/Pc1CvzFkFFGa3E1jU0joVjprOuNWUQ nPQCltrUVgMbrUw== X-Received: from qknqz23.prod.google.com ([2002:a05:620a:8c17:b0:934:b322:8e9f]) (user=edumazet job=prod-delivery.src-stubby-dispatcher) by 2002:a05:620a:a0cc:10b0:930:a26a:fb2a with SMTP id af79cd13be357-939137af782mr418758685a.2.1787906741894; Fri, 28 Aug 2026 01:45:41 -0700 (PDT) Date: Fri, 28 Aug 2026 08:45:28 +0000 In-Reply-To: <20260828084531.1826790-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260828084531.1826790-1-edumazet@google.com> X-Mailer: git-send-email 2.55.0.897.gb25b4bd76c-goog Message-ID: <20260828084531.1826790-3-edumazet@google.com> Subject: [PATCH v2 net 2/5] ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source() From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Ido Schimmel , David Ahern , Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet , Taehee Yoo Content-Type: text/plain; charset="UTF-8" pmc->sflist is read locklessly under rcu_read_lock() by inet6_mc_check() during packet reception in the UDP and RAW multicast receive paths. ip6_mc_source() mutated psl->sl_addr and psl->sl_count in-place when adding or removing a source filter. Additionally, when expanding the filter buffer, newpsl was published via rcu_assign_pointer() before writing the new source into the array. Because 16-byte struct in6_addr writes are not atomic and array shifting is not synchronized with RCU readers, concurrent readers in inet6_mc_check() could read torn IPv6 addresses or observe duplicated/missed source entries. Fix this by switching ip6_mc_source() to copy-on-write RCU updates: allocate and fully populate newpsl before publishing it via rcu_assign_pointer(), and reclaim the old filter via kfree_rcu(), matching ip6_mc_msfilter(). Also remove the now unused IP6_SFBLOCK macro. Fixes: 882ba1f73c06 ("mld: convert ipv6_mc_socklist->sflist to RCU") Signed-off-by: Eric Dumazet Cc: Taehee Yoo --- v2: See https://lore.kernel.org/netdev/CANn89i++X6UUpACK+Bq9d+qbiu1NQ=Ynz75OQgbWjUHNyu-S8Q@mail.gmail.com/ include/net/if_inet6.h | 2 - net/ipv6/mcast.c | 98 ++++++++++++++++++++++++------------------ 2 files changed, 56 insertions(+), 44 deletions(-) diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h index 238ad3349456a3afeab6c02172a9e2d681d2ec9c..795fb41b45f5d10d903de220df3cd0c3798561a0 100644 --- a/include/net/if_inet6.h +++ b/include/net/if_inet6.h @@ -88,8 +88,6 @@ struct ip6_sf_socklist { struct in6_addr sl_addr[] __counted_by(sl_max); }; -#define IP6_SFBLOCK 10 /* allocate this many at once */ - struct ipv6_mc_socklist { struct in6_addr addr; int ifindex; diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c index ec7fac511c8d50da7125ff1c4cd23af46875791d..66f5858e5fea68e27da1f857b5596808632618a3 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -355,12 +355,12 @@ int ip6_mc_source(int add, int omode, struct sock *sk, { struct ipv6_pinfo *inet6 = inet6_sk(sk); struct in6_addr *source, *group; + struct ip6_sf_socklist *newpsl, *psl; struct net *net = sock_net(sk); struct ipv6_mc_socklist *pmc; - struct ip6_sf_socklist *psl; struct inet6_dev *idev; int leavegroup = 0; - int i, j, rv; + int i, j; int err; source = &((struct sockaddr_in6 *)&pgsr->gsr_source)->sin6_addr; @@ -409,13 +409,11 @@ int ip6_mc_source(int add, int omode, struct sock *sk, if (!add) { if (!psl) goto done; /* err = -EADDRNOTAVAIL */ - rv = !0; for (i = 0; i < psl->sl_count; i++) { - rv = !ipv6_addr_equal(&psl->sl_addr[i], source); - if (rv == 0) + if (ipv6_addr_equal(&psl->sl_addr[i], source)) break; } - if (rv) /* source not found */ + if (i == psl->sl_count) /* source not found */ goto done; /* err = -EADDRNOTAVAIL */ /* special case - (INCLUDE, empty) == LEAVE_GROUP */ @@ -424,58 +422,74 @@ int ip6_mc_source(int add, int omode, struct sock *sk, goto done; } + atomic_sub(struct_size(psl, sl_addr, psl->sl_max), + &sk->sk_omem_alloc); + + if (psl->sl_count == 1) { + newpsl = NULL; + } else { + newpsl = sock_kmalloc(sk, struct_size(newpsl, sl_addr, + psl->sl_count - 1), + GFP_KERNEL); + if (!newpsl) { + atomic_add(struct_size(psl, sl_addr, psl->sl_max), + &sk->sk_omem_alloc); + err = -ENOBUFS; + goto done; + } + newpsl->sl_max = psl->sl_count - 1; + newpsl->sl_count = psl->sl_count - 1; + for (j = 0; j < i; j++) + newpsl->sl_addr[j] = psl->sl_addr[j]; + for (j = i + 1; j < psl->sl_count; j++) + newpsl->sl_addr[j - 1] = psl->sl_addr[j]; + } + /* update the interface filter */ ip6_mc_del_src(idev, group, omode, 1, source, 1); - for (j = i+1; j < psl->sl_count; j++) - psl->sl_addr[j-1] = psl->sl_addr[j]; - psl->sl_count--; + rcu_assign_pointer(pmc->sflist, newpsl); + kfree_rcu(psl, rcu); err = 0; goto done; } /* else, add a new source to the filter */ - if (psl && psl->sl_count >= sysctl_mld_max_msf) { + if (psl && psl->sl_count >= READ_ONCE(sysctl_mld_max_msf)) { err = -ENOBUFS; goto done; } - if (!psl || psl->sl_count == psl->sl_max) { - struct ip6_sf_socklist *newpsl; - int count = IP6_SFBLOCK; - - if (psl) - count += psl->sl_max; - newpsl = sock_kmalloc(sk, struct_size(newpsl, sl_addr, count), - GFP_KERNEL); - if (!newpsl) { - err = -ENOBUFS; - goto done; - } - newpsl->sl_max = count; - newpsl->sl_count = count - IP6_SFBLOCK; - if (psl) { - for (i = 0; i < psl->sl_count; i++) - newpsl->sl_addr[i] = psl->sl_addr[i]; - atomic_sub(struct_size(psl, sl_addr, psl->sl_max), - &sk->sk_omem_alloc); + if (psl) { + for (i = 0; i < psl->sl_count; i++) { + if (ipv6_addr_equal(&psl->sl_addr[i], source)) + goto done; /* err = -EADDRNOTAVAIL */ } - rcu_assign_pointer(pmc->sflist, newpsl); - kfree_rcu(psl, rcu); - psl = newpsl; } - rv = 1; /* > 0 for insert logic below if sl_count is 0 */ - for (i = 0; i < psl->sl_count; i++) { - rv = !ipv6_addr_equal(&psl->sl_addr[i], source); - if (rv == 0) /* There is an error in the address. */ - goto done; + + i = psl ? psl->sl_count + 1 : 1; + newpsl = sock_kmalloc(sk, struct_size(newpsl, sl_addr, i), + GFP_KERNEL); + if (!newpsl) { + err = -ENOBUFS; + goto done; } - for (j = psl->sl_count-1; j >= i; j--) - psl->sl_addr[j+1] = psl->sl_addr[j]; - psl->sl_addr[i] = *source; - psl->sl_count++; - err = 0; + newpsl->sl_max = i; + newpsl->sl_count = i; + if (psl) { + for (j = 0; j < psl->sl_count; j++) + newpsl->sl_addr[j] = psl->sl_addr[j]; + } + newpsl->sl_addr[i - 1] = *source; + /* update the interface list */ ip6_mc_add_src(idev, group, omode, 1, source, 1); + + if (psl) + atomic_sub(struct_size(psl, sl_addr, psl->sl_max), + &sk->sk_omem_alloc); + rcu_assign_pointer(pmc->sflist, newpsl); + kfree_rcu(psl, rcu); + err = 0; done: mutex_unlock(&idev->mc_lock); in6_dev_put(idev); -- 2.55.0.897.gb25b4bd76c-goog