xl: Perform minimal validation of virtual disk file while parsing config file

This patch performs some very basic validation on the virtual disk
file passed through the config file.  This validation ensures that we
don't go too far with the initialization like spawn qemu and more
while there could be some potentially fundamental issues.

[ Patch fixed up to work with PHYSTYPE_EMPTY 22808:6ec61438713a -iwj ]

Signed-off-by: Kamala Narasimhan <kamala.narasimhan@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 93a22d2024..6fee2b1a60 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -833,6 +833,31 @@ 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[0] == '\0') && (disk_type == PHYSTYPE_EMPTY) )
+        return 0;
+
+    if ( stat(file_name, &stat_buf) != 0 ) {
+        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "failed to stat %s", file_name);
+        return ERROR_INVAL;
+    }
+    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 ERROR_INVAL;
+        }
+    } else if ( stat_buf.st_size == 0 ) {
+        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "Virtual disk %s size is 0!\n", file_name);
+        return ERROR_INVAL;
+    }
+
+    return 0;
+}
+
 int libxl_device_disk_add(libxl_ctx *ctx, uint32_t domid, libxl_device_disk *disk)
 {
     libxl__gc gc = LIBXL_INIT_GC(ctx);
@@ -843,6 +868,10 @@ int libxl_device_disk_add(libxl_ctx *ctx, uint32_t domid, libxl_device_disk *dis
     libxl__device device;
     int major, minor, rc;
 
+    rc = validate_virtual_disk(ctx, disk->physpath, disk->phystype);
+    if (rc)
+        return rc;
+
     front = flexarray_make(16, 1);
     if (!front) {
         rc = ERROR_NOMEM;