From: Greg KH <gregkh@linuxfoundation.org>
To: Your Real Name <zhutong@amazon.com>
Cc: David Miller <davem@davemloft.net>,
sashal@kernel.org, edumazet@google.com, vvs@virtuozzo.com,
netdev@vger.kernel.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] neighbour: Disregard DEAD dst in neigh_update
Date: Fri, 8 Jan 2021 08:34:16 +0100 [thread overview]
Message-ID: <X/gK+KBlROogPCol@kroah.com> (raw)
In-Reply-To: <20210108023637.GA31904@ucf43ac461c9a53.ant.amazon.com>
On Thu, Jan 07, 2021 at 09:36:37PM -0500, Your Real Name wrote:
> On Tue, Jan 05, 2021 at 04:05:21PM -0800, David Miller wrote:
> >
> >
> > From: Tong Zhu <zhutong@amazon.com>
> > Date: Wed, 30 Dec 2020 17:54:23 -0500
> >
> > > In 4.x kernel a dst in DST_OBSOLETE_DEAD state is associated
> > > with loopback net_device and leads to loopback neighbour. It
> > > leads to an ethernet header with all zero addresses.
> > >
> > > A very troubling case is working with mac80211 and ath9k.
> > > A packet with all zero source MAC address to mac80211 will
> > > eventually fail ieee80211_find_sta_by_ifaddr in ath9k (xmit.c).
> > > As result, ath9k flushes tx queue (ath_tx_complete_aggr) without
> > > updating baw (block ack window), damages baw logic and disables
> > > transmission.
> > >
> > > Signed-off-by: Tong Zhu <zhutong@amazon.com>
> >
> > Please repost with an appropriate Fixes: tag.
> >
> > Thanks.
>
> I had a second thought on this. This fix should go mainline too. This is a
> case we are sending out queued packets when arp reply from the neighbour
> comes in. With 5.x kernel, a dst in DST_OBSOLETE_DEAD state leads to dropping
> of this packet. It is not as bad as with 4.x kernel that may end up with an
> all-zero mac address packet out to ethernet or choking up ath9k when using
> block ack. Dropping the packet is still wrong. I’ll repost as a fix to
> mainline and target backport to 4.x LTS releases.
That's how kernel development works, please read
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how stable kernels are allowed to accept patches.
good luck!
greg k-h
next prev parent reply other threads:[~2021-01-08 7:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-30 22:54 [PATCH] neighbour: Disregard DEAD dst in neigh_update Tong Zhu
2021-01-06 0:05 ` David Miller
2021-01-08 2:36 ` Your Real Name
2021-01-08 7:34 ` Greg KH [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-03-19 18:33 Tong Zhu
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