[xen master] libxl: Check stubdomain kernel & ramdisk presence

[patchbot@xxxxxxx]

commit e235fa2794c95365519eac714d6ea82f8e64752e
Author:     Jason Andryuk <jandryuk@xxxxxxxxx>
AuthorDate: Mon May 18 21:55:03 2020 -0400
Commit:     Wei Liu <wl@xxxxxxx>
CommitDate: Tue May 19 16:19:15 2020 +0100

    libxl: Check stubdomain kernel & ramdisk presence
    
    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@xxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 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;
 
--
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