libxl: Protect access to libxlLogger files hash table

The hash table of log file objects in libxlLogger is not protected against
concurrent access. It is possible for one thread to remove an entry while
another is updating it. Add a mutex to the libxlLogger object and lock it
when accessing the files hash table.

Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

diff --git a/src/libxl/libxl_logger.c b/src/libxl/libxl_logger.c
index d176c2a7c27469426a202a7f74ffe44d7d3c1739..44ee5a95da073812d19812695b6122c16399ad97 100644 (file)
--- a/src/libxl/libxl_logger.c
+++ b/src/libxl/libxl_logger.c
@@ -28,6 +28,7 @@
 #include "util/virfile.h"
 #include "util/virhash.h"
 #include "util/virstring.h"
+#include "util/virthread.h"
 #include "util/virtime.h"
 
 #define VIR_FROM_THIS VIR_FROM_LIBXL
@@ -43,6 +44,7 @@ struct xentoollog_logger_libvirt {
 
     /* map storing the opened fds: "domid" -> FILE* */
     GHashTable *files;
+    virMutex tableLock;
     FILE *defaultLogFile;
 };
 
@@ -85,7 +87,9 @@ libvirt_vmessage(xentoollog_logger *logger_in,
         start = start + 9;
         *end = '\0';
 
+        virMutexLock(&lg->tableLock);
         domainLogFile = virHashLookup(lg->files, start);
+        virMutexUnlock(&lg->tableLock);
         if (domainLogFile)
             logFile = domainLogFile;
 
@@ -155,6 +159,11 @@ libxlLoggerNew(const char *logDir, virLogPriority minLevel)
     if ((logger.defaultLogFile = fopen(path, "a")) == NULL)
         return NULL;
 
+    if (virMutexInit(&logger.tableLock) < 0) {
+        VIR_FORCE_FCLOSE(logger.defaultLogFile);
+        return NULL;
+    }
+
     logger.files = virHashNew(libxlLoggerFileFree);
 
     return XTL_NEW_LOGGER(libvirt, logger);
@@ -167,6 +176,7 @@ libxlLoggerFree(libxlLogger *logger)
     if (logger->defaultLogFile)
         VIR_FORCE_FCLOSE(logger->defaultLogFile);
     g_clear_pointer(&logger->files, g_hash_table_unref);
+    virMutexDestroy(&logger->tableLock);
     xtl_logger_destroy(xtl_logger);
 }
 
@@ -188,7 +198,9 @@ libxlLoggerOpenFile(libxlLogger *logger,
                  path, g_strerror(errno));
         return;
     }
+    virMutexLock(&logger->tableLock);
     ignore_value(virHashAddEntry(logger->files, domidstr, logFile));
+    virMutexUnlock(&logger->tableLock);
 
     /* domain_config is non NULL only when starting a new domain */
     if (domain_config) {
@@ -203,5 +215,7 @@ libxlLoggerCloseFile(libxlLogger *logger, int id)
     g_autofree char *domidstr = NULL;
     domidstr = g_strdup_printf("%d", id);
 
+    virMutexLock(&logger->tableLock);
     ignore_value(virHashRemoveEntry(logger->files, domidstr));
+    virMutexUnlock(&logger->tableLock);
 }