From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: [PATCH] sis900: Allocate rx replacement buffer before rx operation Date: Thu, 26 Apr 2007 19:30:14 -0400 Message-ID: <20070426233014.GB3600@localhost.localdomain> References: <20070420135458.GB16191@hmsreliant.homelinux.net> <462E33A8.5060107@garzik.org> <20070426174736.GC6000@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, davem@davemloft.net, venza@brownhat.org To: Jeff Garzik Return-path: Received: from ra.tuxdriver.com ([70.61.120.52]:4887 "EHLO ra.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753897AbXD0AQy (ORCPT ); Thu, 26 Apr 2007 20:16:54 -0400 Content-Disposition: inline In-Reply-To: <20070426174736.GC6000@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Thu, Apr 26, 2007 at 01:47:36PM -0400, Neil Horman wrote: > On Tue, Apr 24, 2007 at 12:43:20PM -0400, Jeff Garzik wrote: > > Neil Horman wrote: > > >Hey there- > > > The sis900 driver appears to have a bug in which the receive routine > > >passes the skbuff holding the received frame to the network stack before > > >refilling the buffer in the rx ring. If a new skbuff cannot be allocated, > > >the > > >driver simply leaves a hole in the rx ring, which causes the driver to stop > > >receiving frames and become non-recoverable without an rmmod/insmod > > >according to > > >reporters. This patch reverses that order, attempting to allocate a > > >replacement > > >buffer first, and receiving the new frame only if one can be allocated. > > >If no > > >skbuff can be allocated, the current skbuf in the rx ring is recycled, > > >dropping > > >the current frame, but keeping the NIC operational. > > > > > >Thanks & Regards > > >Neil > > > > > > Just found a hole in my last patch. It was reported to me that shortly after we > integrated this patch. The report was of an oops that took place inside of > netif_rx when using the sis900 driver. Looking at my origional patch I noted > that there was a spot between the new skb_alloc and the refill_rx_ring label > where skb got reassigned to the pointer currently held in the rx_ring for the > purposes of receiveing the frame. The result of this is however that the buffer > that gets passed to netif_rx (if it is called), then gets placed right back into > the rx_ring. So if you receive frames fast enough the skb being processed by > the network stack can get corrupted. The reporter is testing out the fix I've > written for this below (I'm not near my hardware at the moment to test myself), > but I wanted to post it for review ASAP. I'll post test results when I hear > them, but I think this is a pretty straightforward fix. It just uses a separate > pointer to do the rx operation, so that we don't improperly reassign the pointer > that we use to refill the rx ring. > > Thanks & Regards > Neil > Test results are back and appear successful. Neil