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Message-Id: <20171211.105308.1899676147655539775.davem@davemloft.net> Date: Mon, 11 Dec 2017 10:53:08 -0500 (EST) From: David Miller <davem@...emloft.net> To: mst@...hat.com Cc: linux-kernel@...r.kernel.org, george.cherian@...ium.com, jasowang@...hat.com, edumazet@...gle.com, netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org Subject: Re: [PATCH] ptr_ring: add barriers From: "Michael S. Tsirkin" <mst@...hat.com> Date: Tue, 5 Dec 2017 21:29:37 +0200 > Users of ptr_ring expect that it's safe to give the > data structure a pointer and have it be available > to consumers, but that actually requires an smb_wmb > or a stronger barrier. > > In absence of such barriers and on architectures that reorder writes, > consumer might read an un=initialized value from an skb pointer stored > in the skb array. This was observed causing crashes. > > To fix, add memory barriers. The barrier we use is a wmb, the > assumption being that producers do not need to read the value so we do > not need to order these reads. > > Reported-by: George Cherian <george.cherian@...ium.com> > Suggested-by: Jason Wang <jasowang@...hat.com> > Signed-off-by: Michael S. Tsirkin <mst@...hat.com> I'm asked for asking for testing feedback and did not get it in a reasonable amount of time. So I'm applying this as-is, and queueing it up for -stable. Thank you.
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