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 6B96D3A0B3D; Mon, 23 Mar 2026 14:07:38 +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=1774274858; cv=none; b=JlLNGj7MoO2DYtIO8+Kt3HzFR0CX8cZpXbT5DdTH2cjJO9CuYpE9+mBcCVcHhkmtMgDsQd+M2eY645S97zDWpnhnGCS7OgK4TICkgFAsOFAoMtIo/BuF8iMpgANcANEZ/6gHFZpqSzWcXr7J1jVB8vL6feG/yc7W3uTI9xX3uzU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774274858; c=relaxed/simple; bh=6rwdOkk4VBCmsI48rAtQQSisi9S7eOl/TjYrf2R31pU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NzE7SxtK08fvJpM1v7WhZsAVCpCxOILuMrBNT8lHuMpYdMubvS6kK4jnMwLB1QhmO5QIDL3U1nPd5YQ59px4LZNWAwffOPsHPQ0cESDvzpkMLiw+sT5tNCvckp4PczCjzJDpUlJI8fJk8sLdTWvKyY7YtFU7DwFmd4arGJxrSu8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=G2nui/UG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="G2nui/UG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2950C4CEF7; Mon, 23 Mar 2026 14:07:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1774274858; bh=6rwdOkk4VBCmsI48rAtQQSisi9S7eOl/TjYrf2R31pU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G2nui/UG3TA9P0AB/IH7N7/8voFSZgQqyVSrBfWKuKB4SRwKmQB8Xj4s3HopeCTid VetlJVdsK9oP2Ps9DKHkxf24JSajAFsHKYBmWO1nYEgVq683KzCWdPLd1GQ4xeHvzy UZfN7/FBhcgi2nXQCKVrfsWzFueJwxtAsa/fnKD0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hyunwoo Kim , Florian Westphal , Sasha Levin Subject: [PATCH 6.18 134/212] netfilter: ctnetlink: fix use-after-free in ctnetlink_dump_exp_ct() Date: Mon, 23 Mar 2026 14:45:55 +0100 Message-ID: <20260323134508.006315803@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260323134503.770111826@linuxfoundation.org> References: <20260323134503.770111826@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hyunwoo Kim [ Upstream commit 5cb81eeda909dbb2def209dd10636b51549a3f8a ] ctnetlink_dump_exp_ct() stores a conntrack pointer in cb->data for the netlink dump callback ctnetlink_exp_ct_dump_table(), but drops the conntrack reference immediately after netlink_dump_start(). When the dump spans multiple rounds, the second recvmsg() triggers the dump callback which dereferences the now-freed conntrack via nfct_help(ct), leading to a use-after-free on ct->ext. The bug is that the netlink_dump_control has no .start or .done callbacks to manage the conntrack reference across dump rounds. Other dump functions in the same file (e.g. ctnetlink_get_conntrack) properly use .start/.done callbacks for this purpose. Fix this by adding .start and .done callbacks that hold and release the conntrack reference for the duration of the dump, and move the nfct_help() call after the cb->args[0] early-return check in the dump callback to avoid dereferencing ct->ext unnecessarily. BUG: KASAN: slab-use-after-free in ctnetlink_exp_ct_dump_table+0x4f/0x2e0 Read of size 8 at addr ffff88810597ebf0 by task ctnetlink_poc/133 CPU: 1 UID: 0 PID: 133 Comm: ctnetlink_poc Not tainted 7.0.0-rc2+ #3 PREEMPTLAZY Call Trace: ctnetlink_exp_ct_dump_table+0x4f/0x2e0 netlink_dump+0x333/0x880 netlink_recvmsg+0x3e2/0x4b0 ? aa_sk_perm+0x184/0x450 sock_recvmsg+0xde/0xf0 Allocated by task 133: kmem_cache_alloc_noprof+0x134/0x440 __nf_conntrack_alloc+0xa8/0x2b0 ctnetlink_create_conntrack+0xa1/0x900 ctnetlink_new_conntrack+0x3cf/0x7d0 nfnetlink_rcv_msg+0x48e/0x510 netlink_rcv_skb+0xc9/0x1f0 nfnetlink_rcv+0xdb/0x220 netlink_unicast+0x3ec/0x590 netlink_sendmsg+0x397/0x690 __sys_sendmsg+0xf4/0x180 Freed by task 0: slab_free_after_rcu_debug+0xad/0x1e0 rcu_core+0x5c3/0x9c0 Fixes: e844a928431f ("netfilter: ctnetlink: allow to dump expectation per master conntrack") Signed-off-by: Hyunwoo Kim Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin --- net/netfilter/nf_conntrack_netlink.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 3a04665adf992..f261dd48973fe 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3211,7 +3211,7 @@ ctnetlink_exp_ct_dump_table(struct sk_buff *skb, struct netlink_callback *cb) { struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh); struct nf_conn *ct = cb->data; - struct nf_conn_help *help = nfct_help(ct); + struct nf_conn_help *help; u_int8_t l3proto = nfmsg->nfgen_family; unsigned long last_id = cb->args[1]; struct nf_conntrack_expect *exp; @@ -3219,6 +3219,10 @@ ctnetlink_exp_ct_dump_table(struct sk_buff *skb, struct netlink_callback *cb) if (cb->args[0]) return 0; + help = nfct_help(ct); + if (!help) + return 0; + rcu_read_lock(); restart: @@ -3248,6 +3252,24 @@ ctnetlink_exp_ct_dump_table(struct sk_buff *skb, struct netlink_callback *cb) return skb->len; } +static int ctnetlink_dump_exp_ct_start(struct netlink_callback *cb) +{ + struct nf_conn *ct = cb->data; + + if (!refcount_inc_not_zero(&ct->ct_general.use)) + return -ENOENT; + return 0; +} + +static int ctnetlink_dump_exp_ct_done(struct netlink_callback *cb) +{ + struct nf_conn *ct = cb->data; + + if (ct) + nf_ct_put(ct); + return 0; +} + static int ctnetlink_dump_exp_ct(struct net *net, struct sock *ctnl, struct sk_buff *skb, const struct nlmsghdr *nlh, @@ -3263,6 +3285,8 @@ static int ctnetlink_dump_exp_ct(struct net *net, struct sock *ctnl, struct nf_conntrack_zone zone; struct netlink_dump_control c = { .dump = ctnetlink_exp_ct_dump_table, + .start = ctnetlink_dump_exp_ct_start, + .done = ctnetlink_dump_exp_ct_done, }; err = ctnetlink_parse_tuple(cda, &tuple, CTA_EXPECT_MASTER, -- 2.51.0