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Date: Fri, 21 Aug 2020 15:10:54 -0600 From: Jens Axboe <axboe@...nel.dk> To: Luke Hsiao <luke.w.hsiao@...il.com>, David Miller <davem@...emloft.net> Cc: netdev@...r.kernel.org, Luke Hsiao <lukehsiao@...gle.com>, Soheil Hassas Yeganeh <soheil@...gle.com>, Arjun Roy <arjunroy@...gle.com>, Eric Dumazet <edumazet@...gle.com>, Jann Horn <jannh@...gle.com> Subject: Re: [PATCH net-next 1/2] io_uring: allow tcp ancillary data for __sys_recvmsg_sock() On 8/20/20 5:49 PM, Luke Hsiao wrote: > From: Luke Hsiao <lukehsiao@...gle.com> > > 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 (https://crbug.com/project-zero/1975). 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 <soheil@...gle.com> > Signed-off-by: Arjun Roy <arjunroy@...gle.com> > Acked-by: Eric Dumazet <edumazet@...gle.com> > Reviewed-by: Jann Horn <jannh@...gle.com> > Signed-off-by: Luke Hsiao <lukehsiao@...gle.com> Reviewed-by: Jens Axboe <axboe@...nel.dk> -- Jens Axboe
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