ptr_ring: add barriers

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[ Upstream commit a8ceb5dbfd ]

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@cavium.com>
Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Michael S. Tsirkin 2017-12-05 21:29:37 +02:00 • committed by Greg Kroah-Hartman

parent b3b56038ba

commit 8b032bde28

1 changed files with 9 additions and 0 deletions

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include/linux/ptr_ring.h

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