Don't set sehash when calling restoreconRecursive

restorecon_recursive updates the SELinux label of the files in the
filesystem, and then attempts to write the xattr "security.sehash" as an
optimization for future restorecons. Writing security.* extended
attributes requires CAP_SYS_ADMIN, which system_server doesn't have (and
shouldn't have).

Suppress the computation and writing of the hash value. It's not
needed.

This bug has been around for a long time, but due to the fix for
bug 62302954, the error message is being generated more frequently
now.

TODO: It would be better if the default for restorecon was to suppress
the hash computation, since otherwise it encourages programs to be
overprivileged with CAP_SYS_ADMIN. I'll plan on doing that in a followup
commit.

Bugs where this error message has been called out:
Bug: 129766333
Bug: 129271240
Bug: 128700692
Bug: 129925723

Test: install an APK and ensure that no "SELinux:  setxattr failed"
    error messages are generated.
Change-Id: I83f4f225e4e73453daea42dbcabf0f8a06d320d6

diff --git a/core/java/android/os/SELinux.java b/core/java/android/os/SELinux.java
index 8ffafe4..86d9f89 100644 (file)
--- a/core/java/android/os/SELinux.java
+++ b/core/java/android/os/SELinux.java
@@ -31,12 +31,15 @@ import java.io.IOException;
 public class SELinux {
     private static final String TAG = "SELinux";
 
-    /** Keep in sync with ./external/libselinux/include/selinux/android.h */
+    /** Keep in sync with ./external/selinux/libselinux/include/selinux/android.h */
     private static final int SELINUX_ANDROID_RESTORECON_NOCHANGE = 1;
     private static final int SELINUX_ANDROID_RESTORECON_VERBOSE = 2;
     private static final int SELINUX_ANDROID_RESTORECON_RECURSE = 4;
     private static final int SELINUX_ANDROID_RESTORECON_FORCE = 8;
     private static final int SELINUX_ANDROID_RESTORECON_DATADATA = 16;
+    private static final int SELINUX_ANDROID_RESTORECON_SKIPCE = 32;
+    private static final int SELINUX_ANDROID_RESTORECON_CROSS_FILESYSTEMS = 64;
+    private static final int SELINUX_ANDROID_RESTORECON_SKIP_SEHASH = 128;
 
     /**
      * Determine whether SELinux is disabled or enabled.
@@ -175,7 +178,8 @@ public class SELinux {
     @UnsupportedAppUsage
     public static boolean restoreconRecursive(File file) {
         try {
-            return native_restorecon(file.getCanonicalPath(), SELINUX_ANDROID_RESTORECON_RECURSE);
+            return native_restorecon(file.getCanonicalPath(),
+                SELINUX_ANDROID_RESTORECON_RECURSE | SELINUX_ANDROID_RESTORECON_SKIP_SEHASH);
         } catch (IOException e) {
             Slog.e(TAG, "Error getting canonical path. Restorecon failed for " +
                     file.getPath(), e);