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 1769A746A for ; Thu, 12 Jan 2023 13:57:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 791D3C433D2; Thu, 12 Jan 2023 13:57:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673531826; bh=Y7EGuV5nDIn9MMkRELJG7wn7Y89H0W8OT48fYQEPeKY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=S1kvQs7hRhI2HyJoARgA0IdRNb/cxFTwJMlwCF67PMI6yY/1hTR0MIsHPhN/lEWNP psfSn13GYOEB+/KCITI14pIm9Zf0oVaKkUrDzrysEc6sSfD3lnxWODvIuT+rSglRVl 5jBTWjud2+HoBoFJqos31Dt6gFCo8um0L1i1k4hA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Frederick Lawler , Jakub Sitnicki , Jakub Kicinski Subject: [PATCH 6.1 10/10] net: sched: disallow noqueue for qdisc classes Date: Thu, 12 Jan 2023 14:56:31 +0100 Message-Id: <20230112135327.411324794@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230112135326.981869724@linuxfoundation.org> References: <20230112135326.981869724@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Frederick Lawler commit 96398560f26aa07e8f2969d73c8197e6a6d10407 upstream. While experimenting with applying noqueue to a classful queue discipline, we discovered a NULL pointer dereference in the __dev_queue_xmit() path that generates a kernel OOPS: # dev=enp0s5 # tc qdisc replace dev $dev root handle 1: htb default 1 # tc class add dev $dev parent 1: classid 1:1 htb rate 10mbit # tc qdisc add dev $dev parent 1:1 handle 10: noqueue # ping -I $dev -w 1 -c 1 1.1.1.1 [ 2.172856] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 2.173217] #PF: supervisor instruction fetch in kernel mode ... [ 2.178451] Call Trace: [ 2.178577] [ 2.178686] htb_enqueue+0x1c8/0x370 [ 2.178880] dev_qdisc_enqueue+0x15/0x90 [ 2.179093] __dev_queue_xmit+0x798/0xd00 [ 2.179305] ? _raw_write_lock_bh+0xe/0x30 [ 2.179522] ? __local_bh_enable_ip+0x32/0x70 [ 2.179759] ? ___neigh_create+0x610/0x840 [ 2.179968] ? eth_header+0x21/0xc0 [ 2.180144] ip_finish_output2+0x15e/0x4f0 [ 2.180348] ? dst_output+0x30/0x30 [ 2.180525] ip_push_pending_frames+0x9d/0xb0 [ 2.180739] raw_sendmsg+0x601/0xcb0 [ 2.180916] ? _raw_spin_trylock+0xe/0x50 [ 2.181112] ? _raw_spin_unlock_irqrestore+0x16/0x30 [ 2.181354] ? get_page_from_freelist+0xcd6/0xdf0 [ 2.181594] ? sock_sendmsg+0x56/0x60 [ 2.181781] sock_sendmsg+0x56/0x60 [ 2.181958] __sys_sendto+0xf7/0x160 [ 2.182139] ? handle_mm_fault+0x6e/0x1d0 [ 2.182366] ? do_user_addr_fault+0x1e1/0x660 [ 2.182627] __x64_sys_sendto+0x1b/0x30 [ 2.182881] do_syscall_64+0x38/0x90 [ 2.183085] entry_SYSCALL_64_after_hwframe+0x63/0xcd ... [ 2.187402] Previously in commit d66d6c3152e8 ("net: sched: register noqueue qdisc"), NULL was set for the noqueue discipline on noqueue init so that __dev_queue_xmit() falls through for the noqueue case. This also sets a bypass of the enqueue NULL check in the register_qdisc() function for the struct noqueue_disc_ops. Classful queue disciplines make it past the NULL check in __dev_queue_xmit() because the discipline is set to htb (in this case), and then in the call to __dev_xmit_skb(), it calls into htb_enqueue() which grabs a leaf node for a class and then calls qdisc_enqueue() by passing in a queue discipline which assumes ->enqueue() is not set to NULL. Fix this by not allowing classes to be assigned to the noqueue discipline. Linux TC Notes states that classes cannot be set to the noqueue discipline. [1] Let's enforce that here. Links: 1. https://linux-tc-notes.sourceforge.net/tc/doc/sch_noqueue.txt Fixes: d66d6c3152e8 ("net: sched: register noqueue qdisc") Cc: stable@vger.kernel.org Signed-off-by: Frederick Lawler Reviewed-by: Jakub Sitnicki Link: https://lore.kernel.org/r/20230109163906.706000-1-fred@cloudflare.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/sched/sch_api.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/net/sched/sch_api.c +++ b/net/sched/sch_api.c @@ -1132,6 +1132,11 @@ skip: return -ENOENT; } + if (new && new->ops == &noqueue_qdisc_ops) { + NL_SET_ERR_MSG(extack, "Cannot assign noqueue to a class"); + return -EINVAL; + } + err = cops->graft(parent, cl, new, &old, extack); if (err) return err;