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From 1e01e2f96fd5e903394eab59365d5363394c8b18 Mon Sep 17 00:00:00 2001
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From: Jon Maloy <jmaloy@redhat.com>
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Date: Tue, 13 Apr 2021 18:59:12 -0400
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Subject: [PATCH 3/5] net: forbid the reentrant RX
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RH-Author: Jon Maloy <jmaloy@redhat.com>
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Message-id: <20210413185912.3811035-2-jmaloy@redhat.com>
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Patchwork-id: 101467
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O-Subject: [RHEL-8.5.0 qemu-kvm PATCH 1/1] net: forbid the reentrant RX
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Bugzilla: 1859175
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Thomas Huth <thuth@redhat.com>
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RH-Acked-by: Xiao Wang <jasowang@redhat.com>
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From: Jason Wang <jasowang@redhat.com>
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The memory API allows DMA into NIC's MMIO area. This means the NIC's
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RX routine must be reentrant. Instead of auditing all the NIC, we can
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simply detect the reentrancy and return early. The queue->delivering
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is set and cleared by qemu_net_queue_deliver() for other queue helpers
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to know whether the delivering in on going (NIC's receive is being
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called). We can check it and return early in qemu_net_queue_flush() to
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forbid reentrant RX.
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Signed-off-by: Jason Wang <jasowang@redhat.com>
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(cherry picked from commit 22dc8663d9fc7baa22100544c600b6285a63c7a3)
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Signed-off-by: Jon Maloy <jmaloy@redhat.com>
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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net/queue.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/net/queue.c b/net/queue.c
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index 61276ca4be..c679d79f4b 100644
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--- a/net/queue.c
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+++ b/net/queue.c
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@@ -250,6 +250,9 @@ void qemu_net_queue_purge(NetQueue *queue, NetClientState *from)
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bool qemu_net_queue_flush(NetQueue *queue)
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{
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+ if (queue->delivering)
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+ return false;
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+
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while (!QTAILQ_EMPTY(&queue->packets)) {
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NetPacket *packet;
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int ret;
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--
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2.27.0
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