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 4FF3A25EF8E; Tue, 11 Mar 2025 15:22:00 +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=1741706520; cv=none; b=SPLbD1jvpVTtjqNcv85ZCmBOh70znbUq/60aGbHRt9bq1ljVMgb49kK1P5q+OaAGBy9uY/MQULoQHmauL7dtYisnM5Ox3yRPMiSztku4gDUqEQNPIBN81vciZZQfur9uY8YoHG+Vj4e9AZ8vKSmIv+8KFAyXcqIe11XcnbRfSJk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741706520; c=relaxed/simple; bh=7m060mJd9MHquR1x3+mZbYJDyrzdWX6zw9NhX7mldD0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=r+PjLCykq/2sRYHsFonz+lUfvlI2HjICTio8dgm4cGfMTR9Gy6K2evxJGoId5WTETfQQY93+EMYLOrb9lavhnLv91Grurj9rKdt6HEAN+T2HfyoDQaNKV7xZt2mb7LaJzPqV06ivU2Qqg02f2xHZTK0P9uFkUCGyyYYlx18ZZMw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=mYEOzpqp; 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="mYEOzpqp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CAC48C4CEE9; Tue, 11 Mar 2025 15:21:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1741706520; bh=7m060mJd9MHquR1x3+mZbYJDyrzdWX6zw9NhX7mldD0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mYEOzpqpZUpPHmgBI+h4kQBuqtOzRxjpacl6cTTLtww0x5fhJlHuhX1zi7+8GtiIy DM/RTf7+fvnGE73jrcbca7pwFoxffHIEwXUKq1hCj3WfJxEJuv8GYOaMrX99FZUoVs bGgY8R5ZzAslykkHaUoJFzSTbkfA5TqeYKfjW+/w= 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 5.10 046/462] net: sched: Disallow replacing of child qdisc from one parent to another Date: Tue, 11 Mar 2025 15:55:12 +0100 Message-ID: <20250311145800.170102564@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250311145758.343076290@linuxfoundation.org> References: <20250311145758.343076290@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 5.10-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 b4e405676600f..238ae7b0ca5ba 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