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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 85ACEC3276C for ; Thu, 2 Jan 2020 22:52:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5866C20848 for ; Thu, 2 Jan 2020 22:52:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578005530; bh=2UtYePbH9BvFGO0ZBIyEg1YlG7Ppbt5KXfY0NKANhfw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=cnbNAe5SIaL4ynt1lLsJXGuPcjmA/8/hliG7Oc9Gndexgj4GMcCOwGYNv43WaAvRq 5s6Zawuoe2lhFFl5Ci2q3n+UPKIUyEzR+8nYnyPWMGGO1gHMEMyz+SFX71sFmV8UtD BF8K8zjQm/IvPSfx4athBxum3uHWuw8L2J3HFT3w= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729530AbgABWwJ (ORCPT ); Thu, 2 Jan 2020 17:52:09 -0500 Received: from mail.kernel.org ([198.145.29.99]:45312 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728308AbgABWXV (ORCPT ); Thu, 2 Jan 2020 17:23:21 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 C862520863; Thu, 2 Jan 2020 22:23:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578003800; bh=2UtYePbH9BvFGO0ZBIyEg1YlG7Ppbt5KXfY0NKANhfw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kxzkNpt1NYNhZ/upM/yWuoTfjf8vX/RD3Ziexh5X/Rxu3YvL+JmIrS/epxhBdeMyI IyCn2WqlmrO6VYQO7Csdlkz3WFKORPZaLFyQH9pxFt6vcQSmniEekUhA6EdWDnaxRE dwg10QFTPfoxylY6wRjGNInTBJMtGjXb94oyl0pw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Eric Dumazet , Christoph Paasch , Neal Cardwell , Jason Baron , Soheil Hassas Yeganeh , Jakub Kicinski Subject: [PATCH 4.19 108/114] tcp: do not send empty skb from tcp_write_xmit() Date: Thu, 2 Jan 2020 23:08:00 +0100 Message-Id: <20200102220040.041353549@linuxfoundation.org> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200102220029.183913184@linuxfoundation.org> References: <20200102220029.183913184@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric Dumazet [ Upstream commit 1f85e6267caca44b30c54711652b0726fadbb131 ] Backport of commit fdfc5c8594c2 ("tcp: remove empty skb from write queue in error cases") in linux-4.14 stable triggered various bugs. One of them has been fixed in commit ba2ddb43f270 ("tcp: Don't dequeue SYN/FIN-segments from write-queue"), but we still have crashes in some occasions. Root-cause is that when tcp_sendmsg() has allocated a fresh skb and could not append a fragment before being blocked in sk_stream_wait_memory(), tcp_write_xmit() might be called and decide to send this fresh and empty skb. Sending an empty packet is not only silly, it might have caused many issues we had in the past with tp->packets_out being out of sync. Fixes: c65f7f00c587 ("[TCP]: Simplify SKB data portion allocation with NETIF_F_SG.") Signed-off-by: Eric Dumazet Cc: Christoph Paasch Acked-by: Neal Cardwell Cc: Jason Baron Acked-by: Soheil Hassas Yeganeh Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv4/tcp_output.c | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2376,6 +2376,14 @@ static bool tcp_write_xmit(struct sock * if (tcp_small_queue_check(sk, skb, 0)) break; + /* Argh, we hit an empty skb(), presumably a thread + * is sleeping in sendmsg()/sk_stream_wait_memory(). + * We do not want to send a pure-ack packet and have + * a strange looking rtx queue with empty packet(s). + */ + if (TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) + break; + if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp))) break;