From ffaa244c76d7baeccab1846b1cae8ca057718f03 Mon Sep 17 00:00:00 2001
From: huangkai <huangkai101@huawei.com>
Date: Sun, 14 Aug 2022 17:32:00 +0800
Subject: [PATCH 18/22] remote_daemon: Don't run virStateCleanup() if
 virStateReload() is still running

When a SIGHUP is received a thread is spawned that runs
virStateReload(). However, if SIGINT is received while the former
thread is still running then we may get into problematic
situation: the cleanup code in main() sees drivers initialized
and thus calls virStateCleanup(). So now we have two threads, one
running virStateReload() the other virStateCleanup(). In this
situation it's very likely that a race condition occurs and
either of threads causes SIGSEGV.

To fix this, unmark drivers as initialized in the
virStateReload() thread for the time the function runs.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2075837
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
---
 src/remote/remote_daemon.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/remote/remote_daemon.c b/src/remote/remote_daemon.c
index a1552800e9..cb93e39413 100644
--- a/src/remote/remote_daemon.c
+++ b/src/remote/remote_daemon.c
@@ -77,7 +77,7 @@ virNetSASLContextPtr saslCtxt = NULL;
 virNetServerProgramPtr remoteProgram = NULL;
 virNetServerProgramPtr qemuProgram = NULL;
 
-volatile bool driversInitialized = false;
+volatile gint driversInitialized = 0;
 
 static void daemonErrorHandler(void *opaque G_GNUC_UNUSED,
                                virErrorPtr err G_GNUC_UNUSED)
@@ -469,7 +469,7 @@ static void daemonReloadHandler(virNetDaemonPtr dmn G_GNUC_UNUSED,
 {
     virThread thr;
 
-    if (!driversInitialized) {
+    if (!g_atomic_int_compare_and_exchange(&driversInitialized, 1, 0)) {
         VIR_WARN("Drivers are not initialized, reload ignored");
         return;
     }
@@ -480,6 +480,9 @@ static void daemonReloadHandler(virNetDaemonPtr dmn G_GNUC_UNUSED,
          * Not much we can do on error here except log it.
          */
         VIR_ERROR(_("Failed to create thread to handle daemon restart"));
+        /* Drivers were initialized at the beginning, otherwise we wouldn't
+         * even get here. */
+        g_atomic_int_set(&driversInitialized, 1);
     }
 }
 
@@ -606,7 +609,7 @@ static void daemonRunStateInit(void *opaque)
         goto cleanup;
     }
 
-    driversInitialized = true;
+    g_atomic_int_set(&driversInitialized, 1);
 
 #ifdef WITH_DBUS
     /* Tie the non-privileged daemons to the session/shutdown lifecycle */
@@ -1206,10 +1209,9 @@ int main(int argc, char **argv) {
 
     virNetlinkEventServiceStopAll();
 
-    if (driversInitialized) {
+    if (g_atomic_int_compare_and_exchange(&driversInitialized, 1, 0)) {
         /* NB: Possible issue with timing window between driversInitialized
          * setting if virNetlinkEventServerStart fails */
-        driversInitialized = false;
         virStateCleanup();
     }
 
-- 
2.33.0

