Re: [Xen-devel] [PATCH] xl: Perform minimal validation of virtual disk file while parsing config file

[Kamala Narasimhan <kamala.narasimhan@xxxxxxxxx>]

Revised patch attached.  Please let me know if I missed a suggestion
or if you have new ones.

Signed-off-by: Kamala Narasimhan <kamala.narasimhan@xxxxxxxxxx>

Kamala

diff -r fe8a177ae9cb tools/libxl/libxl.c
--- a/tools/libxl/libxl.c       Wed Jan 19 15:29:04 2011 +0000
+++ b/tools/libxl/libxl.c       Thu Jan 20 09:37:51 2011 -0500
@@ -826,6 +826,41 @@ skip_autopass:

 
/******************************************************************************/

+static int validate_virtual_disk(libxl_ctx *ctx, char *file_name,
libxl_disk_phystype disk_type)
+{
+    struct stat stat_buf;
+
+    if ( file_name == NULL ) {
+        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "Virtual disk file name is NULL!\n");
+        return 0;
+    }
+
+    /* Return without further validation for empty cdrom drive.
+       Note: Post 4.1 we need to change the interface to handle empty
+       cdrom rather than go with the below assumption.
+     */
+    if ( (strlen(file_name) == 0) && (disk_type == PHYSTYPE_PHY) )
+        return 1;
+
+    if ( stat(file_name, &stat_buf) != 0 ) {
+        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "Stat on virtual disk %s
returned error - \"%s\".\n",
+            file_name, strerror(errno));
+        return 0;
+    }
+    if ( disk_type == PHYSTYPE_PHY ) {
+        if ( !(S_ISBLK(stat_buf.st_mode)) ) {
+            LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "Virtual disk %s is not
a block device!\n",
+                file_name);
+            return 0;
+        }
+    } else if ( stat_buf.st_size == 0 ) {
+        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "Virtual disk %s size is
0!\n", file_name);
+        return 0;
+    }
+
+    return 1;
+}
+
 int libxl_device_disk_add(libxl_ctx *ctx, uint32_t domid,
libxl_device_disk *disk)
 {
     libxl__gc gc = LIBXL_INIT_GC(ctx);
@@ -835,6 +870,9 @@ int libxl_device_disk_add(libxl_ctx *ctx
     int devid;
     libxl__device device;
     int major, minor, rc;
+
+    if ( validate_virtual_disk(ctx, disk->physpath, disk->phystype) == 0 )
+        return ERROR_FAIL;

     front = flexarray_make(16, 1);
     if (!front) {

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