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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CF16C433DF for ; Thu, 13 Aug 2020 00:06:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0F65820855 for ; Thu, 13 Aug 2020 00:06:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597277214; bh=/k+5fqFA2e85qimkdtqp3S+8SyoAlXcnCyoFWgttiuE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ja5MG6yhUqMz4T/8raj85Kuh6rPpoNQYudgqyyJIlrV4JJNZojJa56CRKFFftpmZF x2YdacfeagijdHV3UPWf8eJ6J9od+98vgXvI2AMCTEfcDoqtp2os+lUvfJokjTu+An evFzrgOYuK3tWl3PdLNCu74DILV4QKe2YhlpYk5A= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726557AbgHMAGx (ORCPT ); Wed, 12 Aug 2020 20:06:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:43022 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726078AbgHMAGw (ORCPT ); Wed, 12 Aug 2020 20:06:52 -0400 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6E0E020774; Thu, 13 Aug 2020 00:06:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597277211; bh=/k+5fqFA2e85qimkdtqp3S+8SyoAlXcnCyoFWgttiuE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vy63Gdk44/Tey1L2dsXmoNDAGnlFVT6RQ0vvKuzm52hwXvJDRWOmmSwtkqu1Mulmd RiMIR0+DwuRWMW3iRlz70okoiqrnnYp+sRpYwBkmx2eGG+eNYmAM+zaBLsbgGq6nAl FFIyLSxiR/jg/XTrAsItULx8HsPPOlA8uBAsgxFE= Date: Wed, 12 Aug 2020 20:06:50 -0400 From: Sasha Levin To: Dexuan Cui Cc: "gregkh@linuxfoundation.org" , "edumazet@google.com" , "stable@vger.kernel.org" , Sasha Levin , "w@1wt.eu" , Joseph Salisbury , Michael Kelley , "viro@zeniv.linux.org.uk" , "netdev@vger.kernel.org" , "davem@davemloft.net" , "ohering@suse.com" Subject: Re: [PATCH][for v4.4 only] udp: drop corrupt packets earlier to avoid data corruption Message-ID: <20200813000650.GL2975990@sasha-vm> References: <20200728015505.37830-1-decui@microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Aug 07, 2020 at 06:03:00PM +0000, Dexuan Cui wrote: >> From: Dexuan Cui >> Sent: Monday, July 27, 2020 6:55 PM >> To: gregkh@linuxfoundation.org; edumazet@google.com; >> stable@vger.kernel.org >> Cc: w@1wt.eu; Dexuan Cui ; Joseph Salisbury >> ; Michael Kelley ; >> viro@zeniv.linux.org.uk; netdev@vger.kernel.org; davem@davemloft.net; >> ohering@suse.com >> Subject: [PATCH][for v4.4 only] udp: drop corrupt packets earlier to avoid data >> corruption >> >> The v4.4 stable kernel lacks this bugfix: >> commit 327868212381 ("make skb_copy_datagram_msg() et.al. preserve >> ->msg_iter on error"). >> As a result, the v4.4 kernel can deliver corrupt data to the application >> when a corrupt UDP packet is closely followed by a valid UDP packet: the >> same invocation of the recvmsg() syscall can deliver the corrupt packet's >> UDP payload to the application with the UDP payload length and the >> "from IP/Port" of the valid packet. >> >> Details: >> >> For a UDP packet longer than 76 bytes (see the v5.8-rc6 kernel's >> include/linux/skbuff.h:3951), Linux delays the UDP checksum verification >> until the application invokes the syscall recvmsg(). >> >> In the recvmsg() syscall handler, while Linux is copying the UDP payload >> to the application's memory, it calculates the UDP checksum. If the >> calculated checksum doesn't match the received checksum, Linux drops the >> corrupt UDP packet, and then starts to process the next packet (if any), >> and if the next packet is valid (i.e. the checksum is correct), Linux >> will copy the valid UDP packet's payload to the application's receiver >> buffer. >> >> The bug is: before Linux starts to copy the valid UDP packet, the data >> structure used to track how many more bytes should be copied to the >> application memory is not reset to what it was when the application just >> entered the kernel by the syscall! Consequently, only a small portion or >> none of the valid packet's payload is copied to the application's >> receive buffer, and later when the application exits from the kernel, >> actually most of the application's receive buffer contains the payload >> of the corrupt packet while recvmsg() returns the length of the UDP >> payload of the valid packet. >> >> For the mainline kernel, the bug was fixed in commit 327868212381, >> but unluckily the bugfix is only backported to v4.9+. It turns out >> backporting 327868212381 to v4.4 means that some supporting patches >> must be backported first, so the overall changes seem too big, so the >> alternative is performs the csum validation earlier and drops the >> corrupt packets earlier. >> >> Signed-off-by: Eric Dumazet >> Signed-off-by: Dexuan Cui >> --- >> net/ipv4/udp.c | 3 +-- >> net/ipv6/udp.c | 6 ++---- >> 2 files changed, 3 insertions(+), 6 deletions(-) >> >> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c >> index bb30699..49ab587 100644 >> --- a/net/ipv4/udp.c >> +++ b/net/ipv4/udp.c >> @@ -1589,8 +1589,7 @@ int udp_queue_rcv_skb(struct sock *sk, struct >> sk_buff *skb) >> } >> } >> >> - if (rcu_access_pointer(sk->sk_filter) && >> - udp_lib_checksum_complete(skb)) >> + if (udp_lib_checksum_complete(skb)) >> goto csum_error; >> >> if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) { >> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c >> index 73f1112..2d6703d 100644 >> --- a/net/ipv6/udp.c >> +++ b/net/ipv6/udp.c >> @@ -686,10 +686,8 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct >> sk_buff *skb) >> } >> } >> >> - if (rcu_access_pointer(sk->sk_filter)) { >> - if (udp_lib_checksum_complete(skb)) >> - goto csum_error; >> - } >> + if (udp_lib_checksum_complete(skb)) >> + goto csum_error; >> >> if (sk_rcvqueues_full(sk, sk->sk_rcvbuf)) { >> UDP6_INC_STATS_BH(sock_net(sk), >> -- >> 1.8.3.1 > >+Sasha > >This patch is targeted to the linux-4.4.y branch of the stable tree. Eric, will you ack this (or have a missed a previous ack)? -- Thanks, Sasha