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 2C01E351C39 for ; Thu, 12 Mar 2026 18:35:52 +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=1773340553; cv=none; b=QJwtartEa6X/oFwx2NmXZU0zbgbycOT/RUTsj6nXUrpyv1YjFKTKtDusVfB8QunrKuRBj9AIQsEHUyoMLGNzw5xSMAj3q1f3SQNYIAz5vvAFouthBeQaq3SKAGtxOMcUqscKc26ANxPa5F8yROef0Z8HiAOMcO7gQy6kEhhUgZs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773340553; c=relaxed/simple; bh=sSMVdopdFED0cDsOwwGPaU3TLSS2hd18CMseo5liuPM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=UwanBBdFpBhg0kwAsuQ1K+WBMy7/OVAu6RcxwkLuf0RsrMznGP7E7zZh/+ZJUyn6n85bytFpQBvIQRZ3w0bHpcMS5XdaYmSiCo8fjxwCk7UHRyszZWeaWnAB6UC0Zf/HGAGagRGtof8HSt+PB53yg1cJnXKRdY3DDppMHD2d7Zs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ov8RMgFD; 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="Ov8RMgFD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1C882C4CEF7; Thu, 12 Mar 2026 18:35:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773340552; bh=sSMVdopdFED0cDsOwwGPaU3TLSS2hd18CMseo5liuPM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ov8RMgFDBYEv5vIHHWkSM8vDtlD4G9uAqq4HJscrkmZFdg1EBZW3e26UEvLPSyC+c FwFb1IDeww1grPbfvnuLfMIlhTosWe+kJdc/dw8of2/GxXsGefP1Jz7EgXVGJwf1ye unV/HAEtVKlwdLCAMRn+pEDUoYNEnzEbQXoEQRrlfH+jKOto0jMHPpB8jBDGQo1upC eC7CKRMgeeca+eefezCLTg4TlreXv2egiUY8QpfUdPTvU2Edcj4ij6BbxxPknaovRw E2F84uegE3B5Dy+wUjMk4zn++S5IDMgzn0tzG4HZiXT3n8muq0Bl6jZwe2UcGm2qoI On9JmN3ITAaDg== From: Sasha Levin To: stable@vger.kernel.org Cc: Victor Nogueira , GangMin Kim , Jamal Hadi Salim , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15.y] net/sched: Only allow act_ct to bind to clsact/ingress qdiscs and shared blocks Date: Thu, 12 Mar 2026 14:35:50 -0400 Message-ID: <20260312183550.1823006-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2026031222-subway-snowy-9a66@gregkh> References: <2026031222-subway-snowy-9a66@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Victor Nogueira [ Upstream commit 11cb63b0d1a0685e0831ae3c77223e002ef18189 ] As Paolo said earlier [1]: "Since the blamed commit below, classify can return TC_ACT_CONSUMED while the current skb being held by the defragmentation engine. As reported by GangMin Kim, if such packet is that may cause a UaF when the defrag engine later on tries to tuch again such packet." act_ct was never meant to be used in the egress path, however some users are attaching it to egress today [2]. Attempting to reach a middle ground, we noticed that, while most qdiscs are not handling TC_ACT_CONSUMED, clsact/ingress qdiscs are. With that in mind, we address the issue by only allowing act_ct to bind to clsact/ingress qdiscs and shared blocks. That way it's still possible to attach act_ct to egress (albeit only with clsact). [1] https://lore.kernel.org/netdev/674b8cbfc385c6f37fb29a1de08d8fe5c2b0fbee.1771321118.git.pabeni@redhat.com/ [2] https://lore.kernel.org/netdev/cc6bfb4a-4a2b-42d8-b9ce-7ef6644fb22b@ovn.org/ Reported-by: GangMin Kim Fixes: 3f14b377d01d ("net/sched: act_ct: fix skb leak and crash on ooo frags") CC: stable@vger.kernel.org Signed-off-by: Victor Nogueira Acked-by: Jamal Hadi Salim Link: https://patch.msgid.link/20260225134349.1287037-1-victor@mojatatu.com Signed-off-by: Jakub Kicinski [ adjusted flag bit position and dropped TCA_ACT_FLAGS_AT_INGRESS ] Signed-off-by: Sasha Levin --- include/net/act_api.h | 1 + net/sched/act_ct.c | 6 ++++++ net/sched/cls_api.c | 7 +++++++ 3 files changed, 14 insertions(+) diff --git a/include/net/act_api.h b/include/net/act_api.h index 5cd184ae91cc6..8172e22c8ee65 100644 --- a/include/net/act_api.h +++ b/include/net/act_api.h @@ -65,6 +65,7 @@ struct tc_action { #define TCA_ACT_FLAGS_BIND (1U << (TCA_ACT_FLAGS_USER_BITS + 1)) #define TCA_ACT_FLAGS_REPLACE (1U << (TCA_ACT_FLAGS_USER_BITS + 2)) #define TCA_ACT_FLAGS_NO_RTNL (1U << (TCA_ACT_FLAGS_USER_BITS + 3)) +#define TCA_ACT_FLAGS_AT_INGRESS_OR_CLSACT (1U << (TCA_ACT_FLAGS_USER_BITS + 4)) /* Update lastuse only if needed, to avoid dirtying a cache line. * We use a temp variable to avoid fetching jiffies twice. diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c index d50977ef83c67..171ebf4594793 100644 --- a/net/sched/act_ct.c +++ b/net/sched/act_ct.c @@ -1273,6 +1273,12 @@ static int tcf_ct_init(struct net *net, struct nlattr *nla, return -EINVAL; } + if (bind && !(flags & TCA_ACT_FLAGS_AT_INGRESS_OR_CLSACT)) { + NL_SET_ERR_MSG_MOD(extack, + "Attaching ct to a non ingress/clsact qdisc is unsupported"); + return -EOPNOTSUPP; + } + err = nla_parse_nested(tb, TCA_CT_MAX, nla, ct_policy, extack); if (err < 0) return err; diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index a5864ddfb8902..3b12c3534b1b3 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -1934,6 +1934,11 @@ static void tfilter_put(struct tcf_proto *tp, void *fh) tp->ops->put(tp, fh); } +static bool is_ingress_or_clsact(struct tcf_block *block, struct Qdisc *q) +{ + return tcf_block_shared(block) || (q && !!(q->flags & TCQ_F_INGRESS)); +} + static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n, struct netlink_ext_ack *extack) { @@ -2128,6 +2133,8 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n, flags |= TCA_ACT_FLAGS_REPLACE; if (!rtnl_held) flags |= TCA_ACT_FLAGS_NO_RTNL; + if (is_ingress_or_clsact(block, q)) + flags |= TCA_ACT_FLAGS_AT_INGRESS_OR_CLSACT; err = tp->ops->change(net, skb, tp, cl, t->tcm_handle, tca, &fh, flags, extack); if (err == 0) { -- 2.51.0