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Date:   Fri, 21 Aug 2020 15:10:54 -0600
From:   Jens Axboe <>
To:     Luke Hsiao <>,
        David Miller <>
Cc:, Luke Hsiao <>,
        Soheil Hassas Yeganeh <>,
        Arjun Roy <>,
        Eric Dumazet <>,
        Jann Horn <>
Subject: Re: [PATCH net-next 1/2] io_uring: allow tcp ancillary data for

On 8/20/20 5:49 PM, Luke Hsiao wrote:
> From: Luke Hsiao <>
> For TCP tx zero-copy, the kernel notifies the process of completions by
> queuing completion notifications on the socket error queue. This patch
> allows reading these notifications via recvmsg to support TCP tx
> zero-copy.
> Ancillary data was originally disallowed due to privilege escalation
> via io_uring's offloading of sendmsg() onto a kernel thread with kernel
> credentials ( So, we must ensure
> that the socket type is one where the ancillary data types that are
> delivered on recvmsg are plain data (no file descriptors or values that
> are translated based on the identity of the calling process).
> This was tested by using io_uring to call recvmsg on the MSG_ERRQUEUE
> with tx zero-copy enabled. Before this patch, we received -EINVALID from
> this specific code path. After this patch, we could read tcp tx
> zero-copy completion notifications from the MSG_ERRQUEUE.
> Signed-off-by: Soheil Hassas Yeganeh <>
> Signed-off-by: Arjun Roy <>
> Acked-by: Eric Dumazet <>
> Reviewed-by: Jann Horn <>
> Signed-off-by: Luke Hsiao <>

Reviewed-by: Jens Axboe <>

Jens Axboe

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