[Xen-devel] [PATCH] libxc: don't fail domain creation when unpacking initrd fails

["Jan Beulich" <JBeulich@xxxxxxxx>]

At least Linux kernels have been able to work with gzip-ed initrd for
quite some time; initrd compressed with other methods aren't even being
attempted to unpack. Furthermore the unzip-ing routine used here isn't
capable of dealing with various forms of concatenated files, each of
which was gzip-ed separately (it is this particular case which has been
the source of observed VM creation failures).

Hence, if unpacking fails, simply hand the the compressed blob to the
guest as is.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
I'm not intending to request this to go into 4.10, but I certainly
wouldn't mind. I would appreciate though if I could at least get some
initial feedback earlier than when 4.10 branches off, as we will want
to use a backport of this in our trees, which I'd prefer to be in
line with what is eventually going to go into master.

--- a/tools/libxc/include/xc_dom.h
+++ b/tools/libxc/include/xc_dom.h
@@ -291,7 +291,6 @@ int xc_dom_mem_init(struct xc_dom_image
 int xc_dom_kernel_check_size(struct xc_dom_image *dom, size_t sz);
 int xc_dom_kernel_max_size(struct xc_dom_image *dom, size_t sz);
 
-int xc_dom_ramdisk_check_size(struct xc_dom_image *dom, size_t sz);
 int xc_dom_ramdisk_max_size(struct xc_dom_image *dom, size_t sz);
 
 int xc_dom_devicetree_max_size(struct xc_dom_image *dom, size_t sz);
--- a/tools/libxc/xc_dom_core.c
+++ b/tools/libxc/xc_dom_core.c
@@ -314,7 +314,8 @@ int xc_dom_kernel_check_size(struct xc_d
     return 0;
 }
 
-int xc_dom_ramdisk_check_size(struct xc_dom_image *dom, size_t sz)
+static int xc_dom_ramdisk_check_size(struct xc_dom_image *dom, size_t sz,
+                                     size_t raw)
 {
     /* No limit */
     if ( !dom->max_ramdisk_size )
@@ -322,8 +323,9 @@ int xc_dom_ramdisk_check_size(struct xc_
 
     if ( sz > dom->max_ramdisk_size )
     {
-        xc_dom_panic(dom->xch, XC_INVALID_KERNEL,
-                     "ramdisk image too large");
+        if ( raw > dom->max_ramdisk_size )
+            xc_dom_panic(dom->xch, XC_INVALID_KERNEL,
+                         "ramdisk image too large");
         return 1;
     }
 
@@ -999,13 +1001,13 @@ static int xc_dom_build_ramdisk(struct x
     {
         unziplen = xc_dom_check_gzip(dom->xch,
                                      dom->ramdisk_blob, dom->ramdisk_size);
-        if ( xc_dom_ramdisk_check_size(dom, unziplen) != 0 )
+        if ( xc_dom_ramdisk_check_size(dom, unziplen, dom->ramdisk_size) != 0 )
             unziplen = 0;
     }
     else
         unziplen = 0;
 
-    ramdisklen = unziplen ? unziplen : dom->ramdisk_size;
+    ramdisklen = max(unziplen, dom->ramdisk_size);
 
     if ( xc_dom_alloc_segment(dom, &dom->ramdisk_seg, "ramdisk",
                               dom->ramdisk_seg.vstart, ramdisklen) != 0 )
@@ -1017,14 +1019,15 @@ static int xc_dom_build_ramdisk(struct x
                   __FUNCTION__);
         goto err;
     }
-    if ( unziplen )
+    if ( !unziplen ||
+         xc_dom_do_gunzip(dom->xch, dom->ramdisk_blob, dom->ramdisk_size,
+                          ramdiskmap, unziplen) == -1 )
     {
-        if ( xc_dom_do_gunzip(dom->xch, dom->ramdisk_blob, dom->ramdisk_size,
-                              ramdiskmap, ramdisklen) == -1 )
-            goto err;
-    }
-    else
         memcpy(ramdiskmap, dom->ramdisk_blob, dom->ramdisk_size);
+        if ( unziplen > dom->ramdisk_size )
+            memset(ramdiskmap + dom->ramdisk_size, 0,
+                   unziplen - dom->ramdisk_size);
+    }
 
     return 0;
 




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