Am.java: Use write-only file descriptors

Use write only file descriptors for am commands. Having read-write
file descriptors isn't needed, and not all SELinux app domains have
read access to /data/local/tmp file descriptors.

Addresses the following denial:

  avc: denied { read } for path="/data/local/tmp/foo" dev="dm-2"
  ino=654084 scontext=u:r:system_app:s0
  tcontext=u:object_r:shell_data_file:s0 tclass=file permissive=0

Steps to reproduce:

  adb shell ps | grep settings
  adb shell am dumpheap PID_FROM_ABOVE /data/local/tmp/settings.hat

Expected:
1) command works

Actual:
1) SELinux denial and no settings.hat output.

Bug: 27472701
Change-Id: Id8df0c5a41046b405444e14c70075c986d9936c3

diff --git a/cmds/am/src/com/android/commands/am/Am.java b/cmds/am/src/com/android/commands/am/Am.java
index df0e5fc..fea6f0e 100644 (file)
--- a/cmds/am/src/com/android/commands/am/Am.java
+++ b/cmds/am/src/com/android/commands/am/Am.java
@@ -606,7 +606,7 @@ public class Am extends BaseCommand {
                             new File(mProfileFile),
                             ParcelFileDescriptor.MODE_CREATE |
                             ParcelFileDescriptor.MODE_TRUNCATE |
-                            ParcelFileDescriptor.MODE_READ_WRITE);
+                            ParcelFileDescriptor.MODE_WRITE_ONLY);
                 } catch (FileNotFoundException e) {
                     System.err.println("Error: Unable to open file: " + mProfileFile);
                     System.err.println("Consider using a file under /data/local/tmp/");
@@ -903,7 +903,7 @@ public class Am extends BaseCommand {
             fd = openForSystemServer(file,
                     ParcelFileDescriptor.MODE_CREATE |
                             ParcelFileDescriptor.MODE_TRUNCATE |
-                            ParcelFileDescriptor.MODE_READ_WRITE);
+                            ParcelFileDescriptor.MODE_WRITE_ONLY);
         } catch (FileNotFoundException e) {
             System.err.println("Error: Unable to open file: " + filename);
             System.err.println("Consider using a file under /data/local/tmp/");
@@ -992,7 +992,7 @@ public class Am extends BaseCommand {
                         new File(profileFile),
                         ParcelFileDescriptor.MODE_CREATE |
                         ParcelFileDescriptor.MODE_TRUNCATE |
-                        ParcelFileDescriptor.MODE_READ_WRITE);
+                        ParcelFileDescriptor.MODE_WRITE_ONLY);
             } catch (FileNotFoundException e) {
                 System.err.println("Error: Unable to open file: " + profileFile);
                 System.err.println("Consider using a file under /data/local/tmp/");
@@ -1052,7 +1052,7 @@ public class Am extends BaseCommand {
             fd = openForSystemServer(file,
                     ParcelFileDescriptor.MODE_CREATE |
                     ParcelFileDescriptor.MODE_TRUNCATE |
-                    ParcelFileDescriptor.MODE_READ_WRITE);
+                    ParcelFileDescriptor.MODE_WRITE_ONLY);
         } catch (FileNotFoundException e) {
             System.err.println("Error: Unable to open file: " + heapFile);
             System.err.println("Consider using a file under /data/local/tmp/");