Return-path: Received: from zeniv.linux.org.uk ([195.92.253.2]:51810 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751636AbcGXTCm (ORCPT ); Sun, 24 Jul 2016 15:02:42 -0400 Date: Sun, 24 Jul 2016 20:02:37 +0100 From: Al Viro To: Christian Lamparter Cc: Alan Curry , linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, alexmcwhirter@triadic.us Subject: Re: PROBLEM: network data corruption (bisected to e5a4b0bb803b) Message-ID: <20160724190237.GP2356@ZenIV.linux.org.uk> (sfid-20160724_210320_354514_4222B2A4) References: <201607240335.u6O3ZE81014171@sdf.org> <1659922.nTqITfJpFk@debian64> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1659922.nTqITfJpFk@debian64> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Sun, Jul 24, 2016 at 07:45:13PM +0200, Christian Lamparter wrote: > > The symptom is that downloaded files (http, ftp, and probably other > > protocols) have small corrupted segments (about 1-2 kilobytes long) in > > random locations. Only downloads that sustain a high speed for at least a > > few seconds are corrupted. Anything small enough to be received in less > > than about 5 seconds is not affected. Can that sucker be reproduced with netcat? That would eliminate all issues with multi-iovec recvmsg(2), narrowing the things down quite bit. Another thing (and if that works, it's *NOT* a proper fix - it would be papering over the problem, but at least it would show where to look for it) - try (on top of mainline) the following delta: diff --git a/net/core/datagram.c b/net/core/datagram.c index b7de71f..0ee5995 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -734,7 +734,7 @@ int skb_copy_and_csum_datagram_msg(struct sk_buff *skb, if (!chunk) return 0; - if (msg_data_left(msg) < chunk) { + if (iov_iter_single_seg_count(&msg->msg_iter) < chunk) { if (__skb_checksum_complete(skb)) goto csum_error; if (skb_copy_datagram_msg(skb, hlen, msg, chunk))