qemu-kvm/kvm-net-Update-MemReentrancyGuard-for-NIC.patch

From d58671091daf8c325a6f1cd87737d94b5fb51d12 Mon Sep 17 00:00:00 2001
From: Jon Maloy <jmaloy@redhat.com>
Date: Thu, 23 Nov 2023 11:30:46 -0500
Subject: [PATCH 2/4] net: Update MemReentrancyGuard for NIC

RH-Author: Jon Maloy <jmaloy@redhat.com>
RH-MergeRequest: 331: net: Provide MemReentrancyGuard * to qemu_new_nic()
RH-Jira: RHEL-7309
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
RH-Acked-by: Jason Wang <jasowang@redhat.com>
RH-Commit: [2/2] b116efe725dd838c2cab9bd2240112f3c6c46d6a (redhat/rhel/src/qemu-kvm/jons-qemu-kvm-2)

Jira: https://issues.redhat.com/browse/RHEL-7309
CVE: CVE-2023-3019
Upstream: Merged

commit 9050f976e447444ea6ee2ba12c9f77e4b0dc54bc
Author: Akihiko Odaki <akihiko.odaki@daynix.com>
Date:   Thu Jun 1 12:18:59 2023 +0900

    net: Update MemReentrancyGuard for NIC

    Recently MemReentrancyGuard was added to DeviceState to record that the
    device is engaging in I/O. The network device backend needs to update it
    when delivering a packet to a device.

    This implementation follows what bottom half does, but it does not add
    a tracepoint for the case that the network device backend started
    delivering a packet to a device which is already engaging in I/O. This
    is because such reentrancy frequently happens for
    qemu_flush_queued_packets() and is insignificant.

    Fixes: CVE-2023-3019
    Reported-by: Alexander Bulekov <alxndr@bu.edu>
    Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
    Acked-by: Alexander Bulekov <alxndr@bu.edu>
    Signed-off-by: Jason Wang <jasowang@redhat.com>

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 include/net/net.h |  1 +
 net/net.c         | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/net/net.h b/include/net/net.h
index 1457b6c014..11d4564ea1 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -112,6 +112,7 @@ struct NetClientState {
 typedef struct NICState {
     NetClientState *ncs;
     NICConf *conf;
+    MemReentrancyGuard *reentrancy_guard;
     void *opaque;
     bool peer_deleted;
 } NICState;
diff --git a/net/net.c b/net/net.c
index 669e194c4b..b3008a52b7 100644
--- a/net/net.c
+++ b/net/net.c
@@ -312,6 +312,7 @@ NICState *qemu_new_nic(NetClientInfo *info,
     nic = g_malloc0(info->size + sizeof(NetClientState) * queues);
     nic->ncs = (void *)nic + info->size;
     nic->conf = conf;
+    nic->reentrancy_guard = reentrancy_guard,
     nic->opaque = opaque;
 
     for (i = 0; i < queues; i++) {
@@ -767,6 +768,7 @@ static ssize_t qemu_deliver_packet_iov(NetClientState *sender,
                                        int iovcnt,
                                        void *opaque)
 {
+    MemReentrancyGuard *owned_reentrancy_guard;
     NetClientState *nc = opaque;
     int ret;
 
@@ -779,12 +781,24 @@ static ssize_t qemu_deliver_packet_iov(NetClientState *sender,
         return 0;
     }
 
+    if (nc->info->type != NET_CLIENT_DRIVER_NIC ||
+        qemu_get_nic(nc)->reentrancy_guard->engaged_in_io) {
+        owned_reentrancy_guard = NULL;
+    } else {
+        owned_reentrancy_guard = qemu_get_nic(nc)->reentrancy_guard;
+        owned_reentrancy_guard->engaged_in_io = true;
+    }
+
     if (nc->info->receive_iov && !(flags & QEMU_NET_PACKET_FLAG_RAW)) {
         ret = nc->info->receive_iov(nc, iov, iovcnt);
     } else {
         ret = nc_sendv_compat(nc, iov, iovcnt, flags);
     }
 
+    if (owned_reentrancy_guard) {
+        owned_reentrancy_guard->engaged_in_io = false;
+    }
+
     if (ret == 0) {
         nc->receive_disabled = 1;
     }
-- 
2.41.0