storage: Avoid memory leak on metadata fetching

Getting metadata on storage allocates a memory (path) which need to
be freed after use otherwise it gets leaked. This means after use of
virStorageFileGetMetadataFromFD or virStorageFileGetMetadata one
must call virStorageFileFreeMetadata to free it. This function frees
structure internals and structure itself.

cfg.mk

@@ -156,6 +156,7 @@ useless_free_options =				\
   --name=virSecretDefFree			\
   --name=virStorageEncryptionFree		\
   --name=virStorageEncryptionSecretFree		\
+  --name=virStorageFileFreeMetadata		\
   --name=virStoragePoolDefFree			\
   --name=virStoragePoolObjFree			\
   --name=virStoragePoolSourceFree		\

src/conf/domain_conf.c

@@ -11049,10 +11049,16 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
     int ret = -1;
     size_t depth = 0;
     char *nextpath = NULL;
+    virStorageFileMetadata *meta;
 
     if (!disk->src || disk->type == VIR_DOMAIN_DISK_TYPE_NETWORK)
         return 0;
 
+    if (VIR_ALLOC(meta) < 0) {
+        virReportOOMError();
+        return ret;
+    }
+
     if (disk->driverType) {
         const char *formatStr = disk->driverType;
         if (STREQ(formatStr, "aio"))
@@ -11078,7 +11084,6 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
     paths = virHashCreate(5, NULL);
 
     do {
-        virStorageFileMetadata meta;
         const char *path = nextpath ? nextpath : disk->src;
         int fd;
 
@@ -11106,7 +11111,7 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
             }
         }
 
-        if (virStorageFileGetMetadataFromFD(path, fd, format, &meta) < 0) {
+        if (virStorageFileGetMetadataFromFD(path, fd, format, meta) < 0) {
             VIR_FORCE_CLOSE(fd);
             goto cleanup;
         }
@@ -11120,16 +11125,18 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
             goto cleanup;
 
         depth++;
-        nextpath = meta.backingStore;
+        VIR_FREE(nextpath);
+        nextpath = meta->backingStore;
+        meta->backingStore = NULL;
 
         /* Stop iterating if we reach a non-file backing store */
-        if (nextpath && !meta.backingStoreIsFile) {
+        if (nextpath && !meta->backingStoreIsFile) {
             VIR_DEBUG("Stopping iteration on non-file backing store: %s",
                       nextpath);
             break;
         }
 
-        format = meta.backingStoreFormat;
+        format = meta->backingStoreFormat;
 
         if (format == VIR_STORAGE_FILE_AUTO &&
             !allowProbing)
@@ -11145,6 +11152,7 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
 cleanup:
     virHashFree(paths);
     VIR_FREE(nextpath);
+    virStorageFileFreeMetadata(meta);
 
     return ret;
 }

src/libvirt_private.syms

@@ -940,6 +940,7 @@ virStorageGenerateQcowPassphrase;
 # storage_file.h
 virStorageFileFormatTypeFromString;
 virStorageFileFormatTypeToString;
+virStorageFileFreeMetadata;
 virStorageFileGetMetadata;
 virStorageFileGetMetadataFromFD;
 virStorageFileIsSharedFS;

src/storage/storage_backend_fs.c

@@ -61,8 +61,14 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
                              unsigned long long *capacity,
                              virStorageEncryptionPtr *encryption)
 {
-    int fd, ret;
-    virStorageFileMetadata meta;
+    int fd = -1;
+    int ret = -1;
+    virStorageFileMetadata *meta;
+
+    if (VIR_ALLOC(meta) < 0) {
+        virReportOOMError();
+        return ret;
+    }
 
     *backingStore = NULL;
     *backingStoreFormat = VIR_STORAGE_FILE_AUTO;
@@ -71,36 +77,33 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
 
     if ((ret = virStorageBackendVolOpenCheckMode(target->path,
                                         VIR_STORAGE_VOL_FS_REFRESH_FLAGS)) < 0)
-        return ret; /* Take care to propagate ret, it is not always -1 */
+        goto error; /* Take care to propagate ret, it is not always -1 */
     fd = ret;
 
     if ((ret = virStorageBackendUpdateVolTargetInfoFD(target, fd,
                                                       allocation,
                                                       capacity)) < 0) {
-        VIR_FORCE_CLOSE(fd);
-        return ret;
+        goto error;
     }
 
-    memset(&meta, 0, sizeof(meta));
-
     if ((target->format = virStorageFileProbeFormatFromFD(target->path, fd)) < 0) {
-        VIR_FORCE_CLOSE(fd);
-        return -1;
+        ret = -1;
+        goto error;
     }
 
     if (virStorageFileGetMetadataFromFD(target->path, fd,
                                         target->format,
-                                        &meta) < 0) {
-        VIR_FORCE_CLOSE(fd);
-        return -1;
+                                        meta) < 0) {
+        ret = -1;
+        goto error;
     }
 
     VIR_FORCE_CLOSE(fd);
 
-    if (meta.backingStore) {
-        *backingStore = meta.backingStore;
-        meta.backingStore = NULL;
-        if (meta.backingStoreFormat == VIR_STORAGE_FILE_AUTO) {
+    if (meta->backingStore) {
+        *backingStore = meta->backingStore;
+        meta->backingStore = NULL;
+        if (meta->backingStoreFormat == VIR_STORAGE_FILE_AUTO) {
             if ((ret = virStorageFileProbeFormat(*backingStore)) < 0) {
                 /* If the backing file is currently unavailable, only log an error,
                  * but continue. Returning -1 here would disable the whole storage
@@ -114,18 +117,17 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
                 ret = 0;
             }
         } else {
-            *backingStoreFormat = meta.backingStoreFormat;
+            *backingStoreFormat = meta->backingStoreFormat;
             ret = 0;
         }
     } else {
-        VIR_FREE(meta.backingStore);
         ret = 0;
     }
 
-    if (capacity && meta.capacity)
-        *capacity = meta.capacity;
+    if (capacity && meta->capacity)
+        *capacity = meta->capacity;
 
-    if (encryption != NULL && meta.encrypted) {
+    if (encryption != NULL && meta->encrypted) {
         if (VIR_ALLOC(*encryption) < 0) {
             virReportOOMError();
             goto cleanup;
@@ -147,11 +149,17 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
          */
     }
 
+    virStorageFileFreeMetadata(meta);
+
     return ret;
 
+error:
+    VIR_FORCE_CLOSE(fd);
+
 cleanup:
-    VIR_FREE(*backingStore);
-    return -1;
+    virStorageFileFreeMetadata(meta);
+    return ret;
+
 }
 
 #if WITH_STORAGE_FS

src/util/storage_file.c

@@ -819,6 +819,8 @@ virStorageFileProbeFormat(const char *path)
  * it indicates the image didn't specify an explicit format for its
  * backing store. Callers are advised against probing for the
  * backing store format in this case.
+ *
+ * Caller MUST free @meta after use via virStorageFileFreeMetadata.
  */
 int
 virStorageFileGetMetadataFromFD(const char *path,
@@ -892,6 +894,8 @@ cleanup:
  * it indicates the image didn't specify an explicit format for its
  * backing store. Callers are advised against probing for the
  * backing store format in this case.
+ *
+ * Caller MUST free @meta after use via virStorageFileFreeMetadata.
  */
 int
 virStorageFileGetMetadata(const char *path,
@@ -912,6 +916,20 @@ virStorageFileGetMetadata(const char *path,
     return ret;
 }
 
+/**
+ * virStorageFileFreeMetadata:
+ *
+ * Free pointers in passed structure and structure itself.
+ */
+void
+virStorageFileFreeMetadata(virStorageFileMetadata *meta)
+{
+    if (!meta)
+        return;
+
+    VIR_FREE(meta->backingStore);
+    VIR_FREE(meta);
+}
 
 #ifdef __linux__
 

src/util/storage_file.h

@@ -70,6 +70,8 @@ int virStorageFileGetMetadataFromFD(const char *path,
                                     int format,
                                     virStorageFileMetadata *meta);
 
+void virStorageFileFreeMetadata(virStorageFileMetadata *meta);
+
 enum {
     VIR_STORAGE_FILE_SHFS_NFS = (1 << 0),
     VIR_STORAGE_FILE_SHFS_GFS2 = (1 << 1),