From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f53.google.com (mail-wr1-f53.google.com [209.85.221.53]) (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 7A9E144A41D for ; Fri, 7 Aug 2026 16:44:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786121083; cv=none; b=hagn0nJXRLYi6/UgFVgfadDjzH1g80BRwHdMJO7t2uVbWNC53lgkxEFqwVLOQwSPZRp2ztgidKGWBMKnxUmfXzEpGiOgf3CztQf9EdfLaynncuy+FYi5TFYPWFlF6MlozT3HkP69daCgD/8lNexgMH/FqEGqRYgQlXMp6oB/Oi0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786121083; c=relaxed/simple; bh=+LbwcBxTcVL6TE8Xa7VF9oYYHSPpansJnznnqPEwo64=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=iS0XsPobQo59fsYyWspUCKjgP2Pdrm1U6qBwaedszQ6yNpb/hwOUKuvmF8lwO+beg785o3VgQ5Ib69pUVSN+pGpvummmt6Xj5xlDPlVCXr5oeK6r/9FHsU2xrQ4j2ZvMoLjC7OQjkPs4xN88mVkMNfCVs67MjMP3M4aNo2sLQuU= 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=E8PSHLQH; arc=none smtp.client-ip=209.85.221.53 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="E8PSHLQH" Received: by mail-wr1-f53.google.com with SMTP id ffacd0b85a97d-480001972b8so486807f8f.2 for ; Fri, 07 Aug 2026 09:44:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1786121079; x=1786725879; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=5vPWw2J266KWoCzUTs7KvPsgaoOdOp2O33Cr+Xyu+Z4=; b=E8PSHLQHGw/j+CuTVIAUl805DcGbM3iUEG+Q0rGXNZncL7mb64gaQJxPAXW1c/IFDn WsVjQbdDOhlsEZW2eBXj/sjRb4ba5FyTwVEC+scdS+h4UdXwMyaSchYYUiOR/TfW4UXG GRUR0VVXHeTjsLzixoECwg9EJw+5t/hXyt0YhcX66bbdXZ8/B2NaA+ckz9vZqHhZ81o0 htYBCUOCSqddVBGlb/pmmL0Qy3wIXiaQxyhgmvT3vVlfF8o4SKiovNP+oQFoBdkvlyDt OrPRdt6Ue/kK2nnr7i/YSLwmdIaHLeKfeVjJkzWUldB9KcepD8AbK5K0nfgasOasMCgu MP9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786121079; x=1786725879; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=5vPWw2J266KWoCzUTs7KvPsgaoOdOp2O33Cr+Xyu+Z4=; b=SH6YKd779UNBcVuPBoRQ/qSmRELK/wE1ZiLqoUS3RGWkiXIV4llA8/NjUNuB7V8Mqh ThtDewbry2oKPaFhCoVceEBeJkKlk/Pd5OWiIOQARW9z4F4oCpcNwqYzlTAqqxtzX46f 5wjNx5F1ovnY/xh7aReoGCLaPxKBNiR0rcjdboR0nBuTEgx6EqJxgePKHgjELJVb4vHj X3lMgAU2bKbKhwudtQC1HVIVwPJbZcljPGpLPLTzJqjVNItTy0adEkHsi6g5fLOfhFyq rLqI7lEelOTyq+RUVk7zHZwy06EOebCGtHfDCw+I+KifFi9i7MyTPgRJVNNv+bw8o9kR aJQw== X-Forwarded-Encrypted: i=1; AHgh+RrlG20xW5wjr8JmiHjanKQcdw3q3Br8USN3prku7k0E5Dsq4egy2AY8p/KhDEVjogW1IVddHC5t5roLNWo=@vger.kernel.org X-Gm-Message-State: AOJu0Yz+wWBTrXvGTFnBWukpS7uMaOvShcEv8aCgb0DbKnjc1FE1hete DPraRBBM0wvrTCtkfjznXqBk6rr1p+QgotAD8iNMX1YnyV+kdk0K3Tz3 X-Gm-Gg: AR+sD10SVY2u/i2XPUP2+oLr9O7OaZhHsiutgl95i9mzGPnNgCCv+cEA9V4I074QMLb BATuV/nPbpW7dxrvrekPo4R5AsPBjiR6egpzA5XQytwBkjbS/b/8HHwXPGjAko0zqtgrvOquU7x nmDItR5bvj6v7IGowUdyUxYph5JWWddpFAphCt/1cSPgMCGJ+pFAcp90A0bat90VUrBI1uy+Iet 4U7weJRtSfofaa8wIMXgqyOIUN8wvgnYduexxXuFjq++UBWi3ziZJy2li1aYUVpOC0HOMktGP5b +aaGXjFjZpm0nYPQ/+2gEUS2m41SA6qyhXQBd7qCLk+IEzR1vMkxEQJEhLrnHJyP00B0P12+BjS QcneXUlMgtZQSJTx7g+NKebxAAPG0rp4YaSiXy3SxhAHHk+Qwsu6cpqxIBMOv7R+XpZGdmoYjW1 K8cpFxXTsJa6ApV3x+l84JcGyWMf4lBGc0hnc4C3phV6rApGwU+6zbo3jME59vWoWJ+XXqDsHDV dRzsvzz9Ke6YqUZ6LcJBPdRY4BW+tiwbfwp X-Received: by 2002:a5d:59c4:0:b0:47f:4919:d5b2 with SMTP id ffacd0b85a97d-47fec4e887dmr36634353f8f.1.1786121078631; Fri, 07 Aug 2026 09:44:38 -0700 (PDT) Received: from pumpkin (82-69-66-36.dsl.in-addr.zen.co.uk. [82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-480021e8cd0sm7470652f8f.17.2026.08.07.09.44.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 07 Aug 2026 09:44:38 -0700 (PDT) Date: Fri, 7 Aug 2026 17:44:37 +0100 From: David Laight To: Breno Leitao Cc: David Ahern , Ido Schimmel , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, stable@vger.kernel.org Subject: Re: [PATCH net 2/2] ipv6: mcast: do not write past optlen in the source filter getsockopt Message-ID: <20260807174437.01bf2e33@pumpkin> In-Reply-To: <20260806-mcast_fix-v1-2-bed0a5518e57@debian.org> References: <20260806-mcast_fix-v1-0-bed0a5518e57@debian.org> <20260806-mcast_fix-v1-2-bed0a5518e57@debian.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 06 Aug 2026 02:42:01 -0700 Breno Leitao wrote: > getsockopt(MCAST_MSFILTER) on an IPv6 socket overruns the caller's buffer > the same way the IPv4 one does. ip6_mc_msfget() fills the source list from > the numsrc left in optval, and nothing compares that against optlen, which > ipv6_get_msfilter() has already reused for the length of the reply. > > Clamp numsrc to what optlen holds, as the IPv4 side now does. Nak, same as IPv4. David > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Cc: stable@vger.kernel.org > Signed-off-by: Breno Leitao > --- > net/ipv6/ipv6_sockglue.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c > index b4c977434c2e0..2c3fbde7cb058 100644 > --- a/net/ipv6/ipv6_sockglue.c > +++ b/net/ipv6/ipv6_sockglue.c > @@ -1012,6 +1012,7 @@ static int ipv6_get_msfilter(struct sock *sk, sockptr_t optval, > { > const int size0 = offsetof(struct group_filter, gf_slist_flex); > struct group_filter gsf; > + unsigned int max_numsrc; > int num; > int err; > > @@ -1021,6 +1022,11 @@ static int ipv6_get_msfilter(struct sock *sk, sockptr_t optval, > return -EFAULT; > if (gsf.gf_group.ss_family != AF_INET6) > return -EADDRNOTAVAIL; > + > + /* Number of sources that would fit in the userspace buffer */ > + max_numsrc = (len - size0) / sizeof(gsf.gf_slist_flex[0]); > + gsf.gf_numsrc = min_t(u32, gsf.gf_numsrc, max_numsrc); > + > num = gsf.gf_numsrc; > sockopt_lock_sock(sk); > err = ip6_mc_msfget(sk, &gsf, optval, size0); > @@ -1041,6 +1047,7 @@ static int compat_ipv6_get_msfilter(struct sock *sk, sockptr_t optval, > { > const int size0 = offsetof(struct compat_group_filter, gf_slist_flex); > struct compat_group_filter gf32; > + unsigned int max_numsrc; > struct group_filter gf; > int err; > int num; > @@ -1050,6 +1057,10 @@ static int compat_ipv6_get_msfilter(struct sock *sk, sockptr_t optval, > > if (copy_from_sockptr(&gf32, optval, size0)) > return -EFAULT; > + > + max_numsrc = (len - size0) / sizeof(gf32.gf_slist_flex[0]); > + gf32.gf_numsrc = min_t(u32, gf32.gf_numsrc, max_numsrc); > + > gf.gf_interface = gf32.gf_interface; > gf.gf_fmode = gf32.gf_fmode; > num = gf.gf_numsrc = gf32.gf_numsrc; >