From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9C42B8F57 for ; Mon, 13 Feb 2023 15:00:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 23842C433EF; Mon, 13 Feb 2023 15:00:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1676300451; bh=neipg8Q+KH/uog9S9t5lAZtzopoMmpOZqaWRCGhXJCY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ucdqj9lqrxRjsvbHx9KQAsmUMHN5EujiPFNMgzRntbu9eJiVtayCT46yW0edTmfFc Wgah3x/V4DFrYZOLoBmJ4gbcGL4t90K1CqCm/0alCzjLblT3yvkRiKJyyJ9RPWr5nP rCbF70971MfJC8cyEqxWiYBfpvckMn2wgW9UwV+s= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Magnus Karlsson , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , "Michael S. Tsirkin" , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.10 020/139] virtio-net: execute xdp_do_flush() before napi_complete_done() Date: Mon, 13 Feb 2023 15:49:25 +0100 Message-Id: <20230213144746.712887375@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230213144745.696901179@linuxfoundation.org> References: <20230213144745.696901179@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Magnus Karlsson [ Upstream commit ad7e615f646c9b5b2cf655cdfb9d91a28db4f25a ] Make sure that xdp_do_flush() is always executed before napi_complete_done(). This is important for two reasons. First, a redirect to an XSKMAP assumes that a call to xdp_do_redirect() from napi context X on CPU Y will be followed by a xdp_do_flush() from the same napi context and CPU. This is not guaranteed if the napi_complete_done() is executed before xdp_do_flush(), as it tells the napi logic that it is fine to schedule napi context X on another CPU. Details from a production system triggering this bug using the veth driver can be found following the first link below. The second reason is that the XDP_REDIRECT logic in itself relies on being inside a single NAPI instance through to the xdp_do_flush() call for RCU protection of all in-kernel data structures. Details can be found in the second link below. Fixes: 186b3c998c50 ("virtio-net: support XDP_REDIRECT") Signed-off-by: Magnus Karlsson Acked-by: Toke Høiland-Jørgensen Link: https://lore.kernel.org/r/20221220185903.1105011-1-sbohrer@cloudflare.com Link: https://lore.kernel.org/all/20210624160609.292325-1-toke@redhat.com/ Acked-by: Michael S. Tsirkin Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/virtio_net.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index c942cd6a2c65..0605c28c684b 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -1525,13 +1525,13 @@ static int virtnet_poll(struct napi_struct *napi, int budget) received = virtnet_receive(rq, budget, &xdp_xmit); + if (xdp_xmit & VIRTIO_XDP_REDIR) + xdp_do_flush(); + /* Out of packets? */ if (received < budget) virtqueue_napi_complete(napi, rq->vq, received); - if (xdp_xmit & VIRTIO_XDP_REDIR) - xdp_do_flush(); - if (xdp_xmit & VIRTIO_XDP_TX) { sq = virtnet_xdp_get_sq(vi); if (virtqueue_kick_prepare(sq->vq) && virtqueue_notify(sq->vq)) { -- 2.39.0