From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 08CC8C433F5 for ; Mon, 24 Jan 2022 19:23:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349972AbiAXTW6 (ORCPT ); Mon, 24 Jan 2022 14:22:58 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:43854 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346786AbiAXTQ3 (ORCPT ); Mon, 24 Jan 2022 14:16:29 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 43A6E61320; Mon, 24 Jan 2022 19:16:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 19921C340E7; Mon, 24 Jan 2022 19:16:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643051788; bh=EmSmdj2VP4v+XjAGMC1f/EnmITY0uUNRs0WMJ0+ywm4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MUdkSmN7OUnMb11iGzNLTWmSg/UZWETPVtorcEmIRrBgXzp2r2TRfQBi4SbQtHbp2 9W5Y4B4MYtHDKxOt/7CKyUns7/X5P69Y2ZH8w6KGrWEC70RwvfKntYLQKV4sE0fV0C td3E+ZCJpViD+DsWMEXMFa9RyGhAj6+3mZxQS8T0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Paul Mackerras , linux-ppp@vger.kernel.org, syzbot , Guillaume Nault , "David S. Miller" , Sasha Levin Subject: [PATCH 4.19 088/239] ppp: ensure minimum packet size in ppp_write() Date: Mon, 24 Jan 2022 19:42:06 +0100 Message-Id: <20220124183945.918547329@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124183943.102762895@linuxfoundation.org> References: <20220124183943.102762895@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-ppp@vger.kernel.org From: Eric Dumazet [ Upstream commit 44073187990d5629804ce0627525f6ea5cfef171 ] It seems pretty clear ppp layer assumed user space would always be kind to provide enough data in their write() to a ppp device. This patch makes sure user provides at least 2 bytes. It adds PPP_PROTO_LEN macro that could replace in net-next many occurrences of hard-coded 2 value. I replaced only one occurrence to ease backports to stable kernels. The bug manifests in the following report: BUG: KMSAN: uninit-value in ppp_send_frame+0x28d/0x27c0 drivers/net/ppp/ppp_generic.c:1740 ppp_send_frame+0x28d/0x27c0 drivers/net/ppp/ppp_generic.c:1740 __ppp_xmit_process+0x23e/0x4b0 drivers/net/ppp/ppp_generic.c:1640 ppp_xmit_process+0x1fe/0x480 drivers/net/ppp/ppp_generic.c:1661 ppp_write+0x5cb/0x5e0 drivers/net/ppp/ppp_generic.c:513 do_iter_write+0xb0c/0x1500 fs/read_write.c:853 vfs_writev fs/read_write.c:924 [inline] do_writev+0x645/0xe00 fs/read_write.c:967 __do_sys_writev fs/read_write.c:1040 [inline] __se_sys_writev fs/read_write.c:1037 [inline] __x64_sys_writev+0xe5/0x120 fs/read_write.c:1037 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x44/0xae Uninit was created at: slab_post_alloc_hook mm/slab.h:524 [inline] slab_alloc_node mm/slub.c:3251 [inline] __kmalloc_node_track_caller+0xe0c/0x1510 mm/slub.c:4974 kmalloc_reserve net/core/skbuff.c:354 [inline] __alloc_skb+0x545/0xf90 net/core/skbuff.c:426 alloc_skb include/linux/skbuff.h:1126 [inline] ppp_write+0x11d/0x5e0 drivers/net/ppp/ppp_generic.c:501 do_iter_write+0xb0c/0x1500 fs/read_write.c:853 vfs_writev fs/read_write.c:924 [inline] do_writev+0x645/0xe00 fs/read_write.c:967 __do_sys_writev fs/read_write.c:1040 [inline] __se_sys_writev fs/read_write.c:1037 [inline] __x64_sys_writev+0xe5/0x120 fs/read_write.c:1037 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82 entry_SYSCALL_64_after_hwframe+0x44/0xae Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet Cc: Paul Mackerras Cc: linux-ppp@vger.kernel.org Reported-by: syzbot Acked-by: Guillaume Nault Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/net/ppp/ppp_generic.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index dc9de8731c564..3f335b57d5cde 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -73,6 +73,8 @@ #define MPHDRLEN 6 /* multilink protocol header length */ #define MPHDRLEN_SSN 4 /* ditto with short sequence numbers */ +#define PPP_PROTO_LEN 2 + /* * An instance of /dev/ppp can be associated with either a ppp * interface unit or a ppp channel. In both cases, file->private_data @@ -502,6 +504,9 @@ static ssize_t ppp_write(struct file *file, const char __user *buf, if (!pf) return -ENXIO; + /* All PPP packets should start with the 2-byte protocol */ + if (count < PPP_PROTO_LEN) + return -EINVAL; ret = -ENOMEM; skb = alloc_skb(count + pf->hdrlen, GFP_KERNEL); if (!skb) @@ -1550,7 +1555,7 @@ ppp_send_frame(struct ppp *ppp, struct sk_buff *skb) } ++ppp->stats64.tx_packets; - ppp->stats64.tx_bytes += skb->len - 2; + ppp->stats64.tx_bytes += skb->len - PPP_PROTO_LEN; switch (proto) { case PPP_IP: -- 2.34.1