xen: patch with XSA-473

This patch only affects ARM, but it's better than setting ARM as knownVulnerabilities.

Arm issues with page refcounting

There are two issues related to the mapping of pages belonging to other
domains: For one, an assertion is wrong there, where the case actually
needs handling.  A NULL pointer de-reference could result on a release
build.  This is CVE-2025-58144.

And then the P2M lock isn't held until a page reference was actually
obtained (or the attempt to do so has failed).  Otherwise the page can
not only change type, but even ownership in between, thus allowing
domain boundaries to be violated.  This is CVE-2025-58145.

Signed-off-by: Fernando Rodrigues <alpha@sigmasquadron.net>

(cherry picked from commit 15968113a2)

pkgs/by-name/xe/xen/package.nix

@@ -24,5 +24,15 @@ buildXenPackage.override { inherit python3Packages; } {
       url = "https://xenbits.xen.org/xsa/xsa472-3.patch";
       hash = "sha256-rikOofQeuLNMBkdQS3xzmwh7BlgMOTMSsQcAOEzNOso=";
     })
+
+    # XSA 473
+    (fetchpatch {
+      url = "https://xenbits.xen.org/xsa/xsa473-1.patch";
+      hash = "sha256-594tTalWcGJSLj3++4QB/ADkHH1qJNrdvg7FG6kOuB8=";
+    })
+    (fetchpatch {
+      url = "https://xenbits.xen.org/xsa/xsa473-2.patch";
+      hash = "sha256-tGuIGxJFBXbckIruSUeTyrM6GabdIj6Pr3cVxeDvNNY=";
+    })
   ];
 }