Merge pull request #20500 from aszlig/qemu-patched-for-nixos-tests

nixos/tests: Use a patched QEMU for testing

nixos/modules/testing/test-instrumentation.nix

@@ -110,6 +110,9 @@ let kernel = config.boot.kernelPackages.kernel; in
 
     networking.usePredictableInterfaceNames = false;
 
+    # Make sure we use a patched QEMU that ignores file ownership.
+    virtualisation.qemu.program = "${pkgs.qemu_test}/bin/qemu-kvm";
+
     # Make it easy to log in as root when running the test interactively.
     users.extraUsers.root.initialHashedPassword = mkOverride 150 "";
 

nixos/modules/virtualisation/qemu-vm.nix

@@ -70,7 +70,7 @@ let
       '')}
 
       # Start QEMU.
-      exec ${pkgs.qemu_kvm}/bin/qemu-kvm \
+      exec ${cfg.qemu.program} \
           -name ${vmName} \
           -m ${toString config.virtualisation.memorySize} \
           ${optionalString (pkgs.stdenv.system == "x86_64-linux") "-cpu kvm64"} \
@@ -299,6 +299,14 @@ in
       };
 
     virtualisation.qemu = {
+      program = mkOption {
+        type = types.path;
+        default = "${pkgs.qemu_kvm}/bin/qemu-kvm";
+        defaultText = "\${pkgs.qemu_kvm}/bin/qemu-kvm";
+        example = literalExample "\${pkgs.qemu_test}/bin/qemu-kvm";
+        description = "The QEMU variant used to start the VM.";
+      };
+
       options =
         mkOption {
           type = types.listOf types.unspecified;

pkgs/applications/virtualization/qemu/default.nix

@@ -11,6 +11,7 @@
 , vncSupport ? true, libjpeg, libpng
 , spiceSupport ? !stdenv.isDarwin, spice, spice_protocol, usbredir
 , x86Only ? false
+, nixosTestRunner ? false
 }:
 
 with stdenv.lib;
@@ -133,7 +134,7 @@ stdenv.mkDerivation rec {
 
     # from http://git.qemu.org/?p=qemu.git;a=patch;h=ff55e94d23ae94c8628b0115320157c763eb3e06
     ./CVE-2016-9102.patch
-  ];
+  ] ++ optional nixosTestRunner ./force-uid0-on-9p.patch;
   hardeningDisable = [ "stackprotector" ];
 
   configureFlags =

pkgs/applications/virtualization/qemu/force-uid0-on-9p.patch

@@ -0,0 +1,48 @@
+diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
+index 845675e..43fa036 100644
+--- a/hw/9pfs/9p-local.c
++++ b/hw/9pfs/9p-local.c
+@@ -128,6 +128,8 @@ static int local_lstat(FsContext *fs_ctx, V9fsPath *fs_path, struct stat *stbuf)
+     if (err) {
+         goto err_out;
+     }
++    stbuf->st_uid = 0;
++    stbuf->st_gid = 0;
+     if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
+         /* Actual credentials are part of extended attrs */
+         uid_t tmp_uid;
+@@ -462,6 +464,16 @@ static ssize_t local_pwritev(FsContext *ctx, V9fsFidOpenState *fs,
+     return ret;
+ }
+ 
++static int maybe_chmod(const char *path, mode_t mode)
++{
++    static char *store_path = NULL;
++    if (store_path == NULL)
++        store_path = getenv("NIX_STORE");
++    if (strncmp(path, store_path, strlen(store_path)) != 0)
++        return chmod(path, mode);
++    return 0;
++}
++
+ static int local_chmod(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
+ {
+     char *buffer;
+@@ -477,7 +489,7 @@ static int local_chmod(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
+     } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) ||
+                (fs_ctx->export_flags & V9FS_SM_NONE)) {
+         buffer = rpath(fs_ctx, path);
+-        ret = chmod(buffer, credp->fc_mode);
++        ret = maybe_chmod(buffer, credp->fc_mode);
+         g_free(buffer);
+     }
+     return ret;
+@@ -621,6 +633,8 @@ static int local_fstat(FsContext *fs_ctx, int fid_type,
+     if (err) {
+         return err;
+     }
++    stbuf->st_uid = 0;
++    stbuf->st_gid = 0;
+     if (fs_ctx->export_flags & V9FS_SM_MAPPED) {
+         /* Actual credentials are part of extended attrs */
+         uid_t tmp_uid;

pkgs/top-level/all-packages.nix

@@ -11470,6 +11470,7 @@ in
   watch = callPackage ../os-specific/linux/procps/watch.nix { };
 
   qemu_kvm = lowPrio (qemu.override { x86Only = true; });
+  qemu_test = lowPrio (qemu.override { x86Only = true; nixosTestRunner = true; });
 
   firmwareLinuxNonfree = callPackage ../os-specific/linux/firmware/firmware-linux-nonfree { };