osl_getVolumeInformation: only stat if necessary

...in the hope that that makes cid#706206 (TOCTOU) go away

Change-Id: I4bc7b44e0268cf5d46aaf55fb4073dcdf67b324c

sal/osl/unx/file_volume.cxx

@@ -211,16 +211,24 @@ oslFileError osl_getVolumeInformation( rtl_uString* ustrDirectoryURL, oslVolumeI
 static oslFileError osl_psz_getVolumeInformation (
     const sal_Char* pszDirectory, oslVolumeInfo* pInfo, sal_uInt32 uFieldMask)
 {
-    __OSL_STATFS_STRUCT sfs;
-
     if (!pInfo)
         return osl_File_E_INVAL;
 
-    __OSL_STATFS_INIT(sfs);
-
     pInfo->uValidFields = 0;
     pInfo->uAttributes  = 0;
+    pInfo->uTotalSpace = 0;
+    pInfo->uFreeSpace  = 0;
+    pInfo->uUsedSpace  = 0;
 
+    if ((uFieldMask
+         & (osl_VolumeInfo_Mask_Attributes | osl_VolumeInfo_Mask_TotalSpace
+            | osl_VolumeInfo_Mask_UsedSpace | osl_VolumeInfo_Mask_FreeSpace
+            | osl_VolumeInfo_Mask_FileSystemName
+            | osl_VolumeInfo_Mask_FileSystemCaseHandling))
+        != 0)
+    {
+        __OSL_STATFS_STRUCT sfs;
+        __OSL_STATFS_INIT(sfs);
         if ((__OSL_STATFS(pszDirectory, &sfs)) < 0)
         {
             oslFileError result = oslTranslateFileError(OSL_FET_ERROR, errno);
@@ -247,10 +255,6 @@ static oslFileError osl_psz_getVolumeInformation (
             pInfo->uValidFields |= osl_VolumeInfo_Mask_Attributes;
         }
 
-    pInfo->uTotalSpace = 0;
-    pInfo->uFreeSpace  = 0;
-    pInfo->uUsedSpace  = 0;
-
 #if defined(__OSL_STATFS_BLKSIZ)
 
         if ((uFieldMask & osl_VolumeInfo_Mask_TotalSpace) ||
@@ -274,8 +278,6 @@ static oslFileError osl_psz_getVolumeInformation (
             pInfo->uValidFields |= osl_VolumeInfo_Mask_FreeSpace;
         }
 
-#endif  /* __OSL_STATFS_BLKSIZ */
-
         if ((pInfo->uValidFields & osl_VolumeInfo_Mask_TotalSpace) &&
             (pInfo->uValidFields & osl_VolumeInfo_Mask_FreeSpace ))
         {
@@ -283,6 +285,26 @@ static oslFileError osl_psz_getVolumeInformation (
             pInfo->uValidFields |= osl_VolumeInfo_Mask_UsedSpace;
         }
 
+#endif  /* __OSL_STATFS_BLKSIZ */
+
+#if defined(__OSL_STATFS_TYPENAME)
+
+        if (uFieldMask & osl_VolumeInfo_Mask_FileSystemName)
+        {
+            rtl_string2UString(
+                &(pInfo->ustrFileSystemName),
+                __OSL_STATFS_TYPENAME(sfs),
+                rtl_str_getLength(__OSL_STATFS_TYPENAME(sfs)),
+                osl_getThreadTextEncoding(),
+                OUSTRING_TO_OSTRING_CVTFLAGS);
+            OSL_ASSERT(pInfo->ustrFileSystemName != 0);
+
+            pInfo->uValidFields |= osl_VolumeInfo_Mask_FileSystemName;
+        }
+
+#endif /* __OSL_STATFS_TYPENAME */
+    }
+
     pInfo->uMaxNameLength = 0;
     if (uFieldMask & osl_VolumeInfo_Mask_MaxNameLength)
     {
@@ -305,23 +327,6 @@ static oslFileError osl_psz_getVolumeInformation (
         }
     }
 
-#if defined(__OSL_STATFS_TYPENAME)
-
-    if (uFieldMask & osl_VolumeInfo_Mask_FileSystemName)
-    {
-        rtl_string2UString(
-            &(pInfo->ustrFileSystemName),
-            __OSL_STATFS_TYPENAME(sfs),
-            rtl_str_getLength(__OSL_STATFS_TYPENAME(sfs)),
-            osl_getThreadTextEncoding(),
-            OUSTRING_TO_OSTRING_CVTFLAGS);
-        OSL_ASSERT(pInfo->ustrFileSystemName != 0);
-
-        pInfo->uValidFields |= osl_VolumeInfo_Mask_FileSystemName;
-    }
-
-#endif /* __OSL_STATFS_TYPENAME */
-
     return osl_File_E_None;
 }