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Date:   Thu, 22 Dec 2022 14:40:15 +0000
To:     Shawn Bohrer <>
Subject: Re: [PATCH] veth: Fix race with AF_XDP exposing old or uninitialized


This patch was applied to netdev/net.git (master)
by Paolo Abeni <>:

On Tue, 20 Dec 2022 12:59:03 -0600 you wrote:
> When AF_XDP is used on on a veth interface the RX ring is updated in two
> steps.  veth_xdp_rcv() removes packet descriptors from the FILL ring
> fills them and places them in the RX ring updating the cached_prod
> pointer.  Later xdp_do_flush() syncs the RX ring prod pointer with the
> cached_prod pointer allowing user-space to see the recently filled in
> descriptors.  The rings are intended to be SPSC, however the existing
> order in veth_poll allows the xdp_do_flush() to run concurrently with
> another CPU creating a race condition that allows user-space to see old
> or uninitialized descriptors in the RX ring.  This bug has been observed
> in production systems.
> [...]

Here is the summary with links:
  - veth: Fix race with AF_XDP exposing old or uninitialized descriptors

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