From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [net-next PATCH] net: ptr_ring: otherwise safe empty checks can overrun array bounds Date: Tue, 2 Jan 2018 19:01:33 +0200 Message-ID: <20180102190107-mutt-send-email-mst@kernel.org> References: <20171228035024.14699.69453.stgit@john-Precision-Tower-5810> <20180102.115219.1101472320429215260.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: john.fastabend@gmail.com, jakub.kicinski@netronome.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, netdev@vger.kernel.org To: David Miller Return-path: Received: from mx1.redhat.com ([209.132.183.28]:37210 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbeABRBf (ORCPT ); Tue, 2 Jan 2018 12:01:35 -0500 Content-Disposition: inline In-Reply-To: <20180102.115219.1101472320429215260.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Jan 02, 2018 at 11:52:19AM -0500, David Miller wrote: > From: John Fastabend > Date: Wed, 27 Dec 2017 19:50:25 -0800 > > > When running consumer and/or producer operations and empty checks in > > parallel its possible to have the empty check run past the end of the > > array. The scenario occurs when an empty check is run while > > __ptr_ring_discard_one() is in progress. Specifically after the > > consumer_head is incremented but before (consumer_head >= ring_size) > > check is made and the consumer head is zeroe'd. > > > > To resolve this, without having to rework how consumer/producer ops > > work on the array, simply add an extra dummy slot to the end of the > > array. Even if we did a rework to avoid the extra slot it looks > > like the normal case checks would suffer some so best to just > > allocate an extra pointer. > > > > Reported-by: Jakub Kicinski > > Fixes: c5ad119fb6c09 ("net: sched: pfifo_fast use skb_array") > > Signed-off-by: John Fastabend > > Applied, thanks John. I think that patch is wrong. I'd rather it got reverted.