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 E00B8154BE0; Mon, 10 Mar 2025 17:46:40 +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=1741628801; cv=none; b=JofxnRXjumlFNqaNqLa1QIXa2beexByfycUfoXpywaQxLRXp+QJQoVkvM6mieoSc9RVhHzwjsk76A7WfbaPt1o5FapTfY+fd0LB9/0Y0A5ZicJC1N6bDgRTSjHX5BsUbkIZwwhyKx6x1XLTq2ocyCS60KFi6gHFFYqYDT7JDoDY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741628801; c=relaxed/simple; bh=9rQCpFQqAUj0aBWElOleShAfgvaqzJZkuRs7GBYCFfU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cDd342soXKzsaJ1xGC2sdKe37g3cZpATt2Y90n7vAo7KEhNZAxh9g35NSLO6231g0cW8javk1NjVTWjjVnvveWVoEIy2mZo2sAZ15lr6PV9URuI3slRGZAjgLXe5bqZqZS/O0/ox7EWeX6ewAYxdMB+gx3PPYFKptLBTUNwYC8U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ok1AZuj7; 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="ok1AZuj7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 67482C4CEE5; Mon, 10 Mar 2025 17:46:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1741628800; bh=9rQCpFQqAUj0aBWElOleShAfgvaqzJZkuRs7GBYCFfU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ok1AZuj7jShkR3AnE7T9NrsuZ0lNM7PUjVZqIrbGhdNCzrh6s5PXO/R7IVUqV6kl3 rPs+d47PKoEFxPMfoGv/0gjM5/QR1qeSh+JuFINEFfeaxmciJtEMj/iwBLxm8h1QXO B3q1nkjobKeW8cQo/FIpVtLOOQAGpkujJGciMB20= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jamal Hadi Salim , Simon Horman , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15 072/620] net: sched: Disallow replacing of child qdisc from one parent to another Date: Mon, 10 Mar 2025 17:58:38 +0100 Message-ID: <20250310170548.420995840@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250310170545.553361750@linuxfoundation.org> References: <20250310170545.553361750@linuxfoundation.org> User-Agent: quilt/0.68 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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jamal Hadi Salim [ Upstream commit bc50835e83f60f56e9bec2b392fb5544f250fb6f ] Lion Ackermann was able to create a UAF which can be abused for privilege escalation with the following script Step 1. create root qdisc tc qdisc add dev lo root handle 1:0 drr step2. a class for packet aggregation do demonstrate uaf tc class add dev lo classid 1:1 drr step3. a class for nesting tc class add dev lo classid 1:2 drr step4. a class to graft qdisc to tc class add dev lo classid 1:3 drr step5. tc qdisc add dev lo parent 1:1 handle 2:0 plug limit 1024 step6. tc qdisc add dev lo parent 1:2 handle 3:0 drr step7. tc class add dev lo classid 3:1 drr step 8. tc qdisc add dev lo parent 3:1 handle 4:0 pfifo step 9. Display the class/qdisc layout tc class ls dev lo class drr 1:1 root leaf 2: quantum 64Kb class drr 1:2 root leaf 3: quantum 64Kb class drr 3:1 root leaf 4: quantum 64Kb tc qdisc ls qdisc drr 1: dev lo root refcnt 2 qdisc plug 2: dev lo parent 1:1 qdisc pfifo 4: dev lo parent 3:1 limit 1000p qdisc drr 3: dev lo parent 1:2 step10. trigger the bug <=== prevented by this patch tc qdisc replace dev lo parent 1:3 handle 4:0 step 11. Redisplay again the qdiscs/classes tc class ls dev lo class drr 1:1 root leaf 2: quantum 64Kb class drr 1:2 root leaf 3: quantum 64Kb class drr 1:3 root leaf 4: quantum 64Kb class drr 3:1 root leaf 4: quantum 64Kb tc qdisc ls qdisc drr 1: dev lo root refcnt 2 qdisc plug 2: dev lo parent 1:1 qdisc pfifo 4: dev lo parent 3:1 refcnt 2 limit 1000p qdisc drr 3: dev lo parent 1:2 Observe that a) parent for 4:0 does not change despite the replace request. There can only be one parent. b) refcount has gone up by two for 4:0 and c) both class 1:3 and 3:1 are pointing to it. Step 12. send one packet to plug echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10001)) step13. send one packet to the grafted fifo echo "" | socat -u STDIN UDP4-DATAGRAM:127.0.0.1:8888,priority=$((0x10003)) step14. lets trigger the uaf tc class delete dev lo classid 1:3 tc class delete dev lo classid 1:1 The semantics of "replace" is for a del/add _on the same node_ and not a delete from one node(3:1) and add to another node (1:3) as in step10. While we could "fix" with a more complex approach there could be consequences to expectations so the patch takes the preventive approach of "disallow such config". Joint work with Lion Ackermann Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Jamal Hadi Salim Reviewed-by: Simon Horman Link: https://patch.msgid.link/20250116013713.900000-1-kuba@kernel.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/sch_api.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c index bf8af9f3f3dce..516874d943cd9 100644 --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -1603,6 +1603,10 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n, q = qdisc_lookup(dev, tcm->tcm_handle); if (!q) goto create_n_graft; + if (q->parent != tcm->tcm_parent) { + NL_SET_ERR_MSG(extack, "Cannot move an existing qdisc to a different parent"); + return -EINVAL; + } if (n->nlmsg_flags & NLM_F_EXCL) { NL_SET_ERR_MSG(extack, "Exclusivity flag on, cannot override"); return -EEXIST; -- 2.39.5