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[libvirt] [PATCH v2] 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.
---
diff to v1:
-Eric's review suggestions taken in

 src/conf/domain_conf.c           |   17 ++++++++---
 src/libvirt_private.syms         |    1 +
 src/storage/storage_backend_fs.c |   53 +++++++++++++++++++++----------------
 src/util/storage_file.c          |   16 +++++++++++
 src/util/storage_file.h          |    2 +
 5 files changed, 61 insertions(+), 28 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 39e59b9..c89c7c6 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -11055,6 +11055,12 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
     int ret = -1;
     size_t depth = 0;
     char *nextpath = NULL;
+    virStorageFileMetadata *meta;
+
+    if (VIR_ALLOC(meta) < 0) {
+        virReportOOMError();
+        return ret;
+    }
 
     if (!disk->src || disk->type == VIR_DOMAIN_DISK_TYPE_NETWORK)
         return 0;
@@ -11084,7 +11090,6 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
     paths = virHashCreate(5, NULL);
 
     do {
-        virStorageFileMetadata meta;
         const char *path = nextpath ? nextpath : disk->src;
         int fd;
 
@@ -11112,7 +11117,7 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
             }
         }
 
-        if (virStorageFileGetMetadataFromFD(path, fd, format, &meta) < 0) {
+        if (virStorageFileGetMetadataFromFD(path, fd, format, meta) < 0) {
             VIR_FORCE_CLOSE(fd);
             goto cleanup;
         }
@@ -11126,16 +11131,17 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
             goto cleanup;
 
         depth++;
-        nextpath = meta.backingStore;
+        VIR_FREE(nextpath);
+        nextpath = meta->backingStore;
 
         /* 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)
@@ -11151,6 +11157,7 @@ int virDomainDiskDefForeachPath(virDomainDiskDefPtr disk,
 cleanup:
     virHashFree(paths);
     VIR_FREE(nextpath);
+    virStorageFileFreeMetadata(meta);
 
     return ret;
 }
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 3237d18..e06c7fc 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -940,6 +940,7 @@ virStorageGenerateQcowPassphrase;
 # storage_file.h
 virStorageFileFormatTypeFromString;
 virStorageFileFormatTypeToString;
+virStorageFileFreeMetadata;
 virStorageFileGetMetadata;
 virStorageFileGetMetadataFromFD;
 virStorageFileIsSharedFS;
diff --git a/src/storage/storage_backend_fs.c b/src/storage/storage_backend_fs.c
index b30e01e..821efb7 100644
--- a/src/storage/storage_backend_fs.c
+++ b/src/storage/storage_backend_fs.c
@@ -61,8 +61,13 @@ virStorageBackendProbeTarget(virStorageVolTargetPtr target,
                              unsigned long long *capacity,
                              virStorageEncryptionPtr *encryption)
 {
-    int fd, ret;
-    virStorageFileMetadata meta;
+    int fd = -1, ret = -1;
+    virStorageFileMetadata *meta;
+
+    if (VIR_ALLOC(meta) < 0) {
+        virReportOOMError();
+        return ret;
+    }
 
     *backingStore = NULL;
     *backingStoreFormat = VIR_STORAGE_FILE_AUTO;
@@ -71,36 +76,33 @@ 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 +116,17 @@ 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 +148,17 @@ 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
diff --git a/src/util/storage_file.c b/src/util/storage_file.c
index 06cabc8..b73412e 100644
--- a/src/util/storage_file.c
+++ b/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 +916,18 @@ virStorageFileGetMetadata(const char *path,
     return ret;
 }
 
+/**
+ * virStorageFileFreeMetadata:
+ *
+ * Free pointers in passed structure, but not memory used by
+ * structure itself.
+ */
+void ATTRIBUTE_NONNULL(1)
+virStorageFileFreeMetadata(virStorageFileMetadata *meta)
+{
+    VIR_FREE(meta->backingStore);
+    VIR_FREE(meta);
+}
 
 #ifdef __linux__
 
diff --git a/src/util/storage_file.h b/src/util/storage_file.h
index f1bdd02..b362796 100644
--- a/src/util/storage_file.h
+++ b/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),
-- 
1.7.5.rc3


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