Use a hash table for storing MCS labels

Instead of using an O(n) efficiency linked list for storing
MCS labels, use a hash table. Instead of having the list
be global, put it in the SELinux driver private data struct
to ensure uniqueness across different instances of the driver.
This also ensures thread safety when multiple hypervisor
drivers are used in the same libvirtd process

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

src/security/security_selinux.c

@@ -32,6 +32,7 @@
 #include "hostusb.h"
 #include "storage_file.h"
 #include "virfile.h"
+#include "virhash.h"
 #include "virrandom.h"
 #include "util.h"
 #include "conf.h"
@@ -50,6 +51,7 @@ struct _virSecuritySELinuxData {
     char *domain_context;
     char *file_context;
     char *content_context;
+    virHashTablePtr mcs;
 };
 
 struct _virSecuritySELinuxCallbackData {
@@ -60,64 +62,31 @@ struct _virSecuritySELinuxCallbackData {
 #define SECURITY_SELINUX_VOID_DOI       "0"
 #define SECURITY_SELINUX_NAME "selinux"
 
-/* TODO
-   The data struct of used mcs should be replaced with a better data structure in the future
-*/
-
-typedef struct virSecuritySELinuxMCS virSecuritySELinuxMCS;
-typedef virSecuritySELinuxMCS *virSecuritySELinuxMCSPtr;
-struct virSecuritySELinuxMCS {
-    char *mcs;
-    virSecuritySELinuxMCSPtr next;
-};
-static virSecuritySELinuxMCSPtr mcsList = NULL;
-
 /*
  * Returns 0 on success, 1 if already reserved, or -1 on fatal error
  */
 static int
-virSecuritySELinuxMCSAdd(const char *mcs)
+virSecuritySELinuxMCSAdd(virSecurityManagerPtr mgr,
+                         const char *mcs)
 {
-    virSecuritySELinuxMCSPtr ptr;
+    virSecuritySELinuxDataPtr data = virSecurityManagerGetPrivateData(mgr);
 
-    for (ptr = mcsList; ptr; ptr = ptr->next) {
+    if (virHashLookup(data->mcs, mcs))
-        if (STREQ(ptr->mcs, mcs))
+        return 1;
-            return 1;
+
-    }
+    if (virHashAddEntry(data->mcs, mcs, (void*)0x1) < 0)
-    if (VIR_ALLOC(ptr) < 0) {
-        virReportOOMError();
         return -1;
-    }
+
-    if (!(ptr->mcs = strdup(mcs))) {
-        virReportOOMError();
-        VIR_FREE(ptr);
-        return -1;
-    }
-    ptr->next = mcsList;
-    mcsList = ptr;
     return 0;
 }
 
-static int
+static void
-virSecuritySELinuxMCSRemove(const char *mcs)
+virSecuritySELinuxMCSRemove(virSecurityManagerPtr mgr,
+                            const char *mcs)
 {
-    virSecuritySELinuxMCSPtr prevptr = NULL;
+    virSecuritySELinuxDataPtr data = virSecurityManagerGetPrivateData(mgr);
-    virSecuritySELinuxMCSPtr ptr = NULL;
 
-    for (ptr = mcsList; ptr; ptr = ptr->next) {
+    virHashRemoveEntry(data->mcs, mcs);
-        if (STREQ(ptr->mcs, mcs)) {
-            if (prevptr)
-                prevptr->next = ptr->next;
-            else {
-                mcsList = ptr->next;
-            }
-            VIR_FREE(ptr->mcs);
-            VIR_FREE(ptr);
-            return 0;
-        }
-        prevptr = ptr;
-    }
-    return -1;
 }
 
 static char *
@@ -191,6 +160,10 @@ virSecuritySELinuxLXCInitialize(virSecurityManagerPtr mgr)
                              selinux_lxc_contexts_path());
         goto error;
     }
+
+    if (!(data->mcs = virHashCreate(10, NULL)))
+        goto error;
+
     virConfFree(selinux_conf);
     return 0;
 
@@ -199,6 +172,7 @@ error:
     VIR_FREE(data->domain_context);
     VIR_FREE(data->file_context);
     VIR_FREE(data->content_context);
+    virHashFree(data->mcs);
     return -1;
 }
 #else
@@ -249,12 +223,16 @@ virSecuritySELinuxQEMUInitialize(virSecurityManagerPtr mgr)
             *ptr = '\0';
     }
 
+    if (!(data->mcs = virHashCreate(10, NULL)))
+        goto error;
+
     return 0;
 
 error:
     VIR_FREE(data->domain_context);
     VIR_FREE(data->file_context);
     VIR_FREE(data->content_context);
+    virHashFree(data->mcs);
     return -1;
 }
 
@@ -355,7 +333,7 @@ virSecuritySELinuxGenSecurityLabel(virSecurityManagerPtr mgr,
                     goto cleanup;
                 }
             }
-            if ((rv = virSecuritySELinuxMCSAdd(mcs)) < 0)
+            if ((rv = virSecuritySELinuxMCSAdd(mgr, mcs)) < 0)
                 goto cleanup;
             if (rv == 0)
                 break;
@@ -452,7 +430,7 @@ virSecuritySELinuxReserveSecurityLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSE
     if (!mcs)
         goto error;
 
-    if ((rv = virSecuritySELinuxMCSAdd(mcs)) < 0)
+    if ((rv = virSecuritySELinuxMCSAdd(mgr, mcs)) < 0)
         goto error;
 
     if (rv == 1) {
@@ -504,6 +482,8 @@ virSecuritySELinuxSecurityDriverClose(virSecurityManagerPtr mgr)
     if (!data)
         return 0;
 
+    virHashFree(data->mcs);
+
     VIR_FREE(data->domain_context);
     VIR_FREE(data->file_context);
     VIR_FREE(data->content_context);
@@ -1195,7 +1175,7 @@ virSecuritySELinuxRestoreSecurityAllLabel(virSecurityManagerPtr mgr ATTRIBUTE_UN
 }
 
 static int
-virSecuritySELinuxReleaseSecurityLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSED,
+virSecuritySELinuxReleaseSecurityLabel(virSecurityManagerPtr mgr,
                                        virDomainDefPtr def)
 {
     const virSecurityLabelDefPtr secdef = &def->seclabel;
@@ -1204,7 +1184,7 @@ virSecuritySELinuxReleaseSecurityLabel(virSecurityManagerPtr mgr ATTRIBUTE_UNUSE
         if (secdef->label != NULL) {
             context_t con = context_new(secdef->label);
             if (con) {
-                virSecuritySELinuxMCSRemove(context_range_get(con));
+                virSecuritySELinuxMCSRemove(mgr, context_range_get(con));
                 context_free(con);
             }
         }