util: ensure all TPM global vars access is protected by lock

The virTPMEmulatorInit method updates various global variables
and holds a lock while doing so. Other methods which access
these variables, however, don't reliably hold locks over all
of their accesses.

Since virTPMEmulatorInit is no longer exported, we can push
the locking up into all the callers and achieve proper safety
for concurrent usage.

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

src/util/virtpm.c

@@ -137,15 +137,17 @@ static int virTPMEmulatorInit(void);
 static char *
 virTPMBinaryGetPath(virTPMBinary binary)
 {
-    char *s;
+    char *s = NULL;
-
-    if (!swtpmBinaries[binary].path && virTPMEmulatorInit() < 0)
-        return NULL;
 
     virMutexLock(&swtpm_tools_lock);
-    s = g_strdup(swtpmBinaries[binary].path);
-    virMutexUnlock(&swtpm_tools_lock);
 
+    if (virTPMEmulatorInit() < 0)
+        goto cleanup;
+
+    s = g_strdup(swtpmBinaries[binary].path);
+
+ cleanup:
+    virMutexUnlock(&swtpm_tools_lock);
     return s;
 }
 
@@ -269,11 +271,8 @@ virTPMGetCaps(virTPMBinaryCapsParse capsParse,
 static int
 virTPMEmulatorInit(void)
 {
-    int ret = -1;
     size_t i;
 
-    virMutexLock(&swtpm_tools_lock);
-
     for (i = 0; i < VIR_TPM_BINARY_LAST; i++) {
         g_autofree char *path = NULL;
         bool findit = swtpmBinaries[i].path == NULL;
@@ -297,18 +296,18 @@ virTPMEmulatorInit(void)
                 virReportSystemError(ENOENT,
                                      _("Unable to find '%s' binary in $PATH"),
                                      virTPMBinaryTypeToString(i));
-                goto cleanup;
+                return -1;
             }
             if (!virFileIsExecutable(path)) {
                 virReportError(VIR_ERR_INTERNAL_ERROR,
                                _("%s is not an executable"),
                                path);
-                goto cleanup;
+                return -1;
             }
             if (stat(path, &swtpmBinaries[i].stat) < 0) {
                 virReportSystemError(errno,
                                      _("Could not stat %s"), path);
-                goto cleanup;
+                return -1;
             }
             swtpmBinaries[i].path = g_steal_pointer(&path);
 
@@ -317,26 +316,29 @@ virTPMEmulatorInit(void)
                                                       swtpmBinaries[i].path,
                                                       swtpmBinaries[i].parm);
                 if (!swtpmBinaries[i].caps)
-                    goto cleanup;
+                    return -1;
             }
         }
     }
 
-    ret = 0;
+    return 0;
-
- cleanup:
-    virMutexUnlock(&swtpm_tools_lock);
-
-    return ret;
 }
 
 static bool
 virTPMBinaryGetCaps(virTPMBinary binary,
                     unsigned int cap)
 {
+    bool ret = false;
+
+    virMutexLock(&swtpm_tools_lock);
+
     if (virTPMEmulatorInit() < 0)
-        return false;
+        goto cleanup;
-    return virBitmapIsBitSet(swtpmBinaries[binary].caps, cap);
+    ret = virBitmapIsBitSet(swtpmBinaries[binary].caps, cap);
+
+ cleanup:
+    virMutexUnlock(&swtpm_tools_lock);
+    return ret;
 }
 
 bool