libxl: restore passing "readonly=" to qemu for SCSI disks

A read-only check was introduced for XSA-142, commit ef6cb76026 ("libxl:
relax readonly check introduced by XSA-142 fix") added the passing of
the extra setting, but commit dab0539568 ("Introduce COLO mode and
refactor relevant function") dropped the passing of the setting again,
quite likely due to improper re-basing.

Restore the readonly= parameter to SCSI disks.  For IDE disks this is
supposed to be rejected; add an assert.  And there is a bare ad-hoc
disk drive string in libxl__build_device_model_args_new, which we also
update.

This is XSA-266.

Reported-by: Andrew Reimers <andrew.reimers@orionvm.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
master commit: dd64d3c41a2d15139c3a35d22d4cb6b78f4c5c59
master date: 2018-06-28 09:05:06 +0200

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 660c01ec056e4056f6a4fe7ac8c80fc7c600052b..72d5e6421841d890f7b2abcbcb4689d9aae45080 100644 (file)
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -771,7 +771,8 @@ static char *qemu_disk_scsi_drive_string(libxl__gc *gc, const char *target_path,
                                          int colo_mode)
 {
     char *drive = NULL;
-    char *common = GCSPRINTF("cache=writeback");
+    char *common = GCSPRINTF("cache=writeback,readonly=%s",
+                             disk->readwrite ? "off" : "on");
     const char *exportname = disk->colo_export;
     const char *active_disk = disk->active_disk;
     const char *hidden_disk = disk->hidden_disk;
@@ -838,6 +839,8 @@ static char *qemu_disk_ide_drive_string(libxl__gc *gc, const char *target_path,
     const char *exportname = disk->colo_export;
     const char *active_disk = disk->active_disk;
     const char *hidden_disk = disk->hidden_disk;
+    
+    assert(disk->readwrite); /* should have been checked earlier */
 
     switch (colo_mode) {
     case LIBXL__COLO_NONE:
@@ -1401,8 +1404,9 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
                 if (strncmp(disks[i].vdev, "sd", 2) == 0) {
                     if (colo_mode == LIBXL__COLO_SECONDARY) {
                         drive = libxl__sprintf
-                            (gc, "if=none,driver=%s,file=%s,id=%s",
-                             format, target_path, disks[i].colo_export);
+                            (gc, "if=none,driver=%s,file=%s,id=%s,readonly=%s",
+                             format, target_path, disks[i].colo_export,
+                             disks[i].readwrite ? "off" : "on");
 
                         flexarray_append(dm_args, "-drive");
                         flexarray_append(dm_args, drive);