[PATCH v7 19/19] libxl: Check stubdomain kernel & ramdisk presence

[Jason Andryuk <jandryuk@gmail.com>]

Just out of context is the following comment for libxl__domain_make:
/* fixme: this function can leak the stubdom if it fails */

When the stubdomain kernel or ramdisk is not present, the domid and
stubdomain name will indeed be leaked.  Avoid the leak by checking the
file presence and erroring out when absent.  It doesn't fix all cases,
but it avoids a big one when using a linux device model stubdomain.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

---
Changes in v6:
 - Add Acked-by: Ian Jackson
---
 tools/libxl/libxl_dm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index 454a2815ed..f2dc5696b9 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -2327,6 +2327,22 @@ void libxl__spawn_stub_dm(libxl__egc *egc, libxl__stub_dm_spawn_state *sdss)
         dm_config->num_vkbs = 1;
     }
 
+    if (guest_config->b_info.stubdomain_kernel &&
+        access(guest_config->b_info.stubdomain_kernel, R_OK) != 0) {
+        LOGED(ERROR, guest_domid, "could not access stubdomain kernel %s",
+              guest_config->b_info.stubdomain_kernel);
+        ret = ERROR_INVAL;
+        goto out;
+    }
+
+    if (guest_config->b_info.stubdomain_ramdisk &&
+        access(guest_config->b_info.stubdomain_ramdisk, R_OK) != 0) {
+        LOGED(ERROR, guest_domid, "could not access stubdomain ramdisk %s",
+              guest_config->b_info.stubdomain_ramdisk);
+        ret = ERROR_INVAL;
+        goto out;
+    }
+
     stubdom_state->pv_kernel.path = guest_config->b_info.stubdomain_kernel;
     stubdom_state->pv_ramdisk.path = guest_config->b_info.stubdomain_ramdisk;
 
-- 
2.25.1