commit 990194fe2fce44496ad8e9f9031d47bf9557127e
author Bart Van Assche <bvanassche@google.com> Thu Mar 10 21:43:22 2022 +0000
committer Bart Van Assche <bvanassche@google.com> Tue Mar 15 23:02:20 2022 +0000
tree 31fac745f026084c048711fe83a33fbed7f0baba
parent f508ede763e8298387c4c7385c049625d7941ce6

Fix cgroup directory permissions

Cgroup attributes are set from three different contexts:
(1) From the process that creates the cgroup directories. These
    processes are /system/bin/init, zygote and zygote64.
(2) From the created process. Some but not all created processes have
    user ID and/or group ID 'system'.
(3) The system_server process modifies certain cgroup attributes from
    other processes.

Allow all processes from the system group, including system_server, to
modify cgroup attributes from other processes. As one can see in
init.rc, that file includes commands for granting the system group
write permission for blkcg attributes. See also
https://cs.android.com/android/platform/superproject/+/master:system/core/rootdir/init.rc

Bug: 213617178
Test: Verified in the Cuttlefish emulator that this patch makes the
Test: io.bfq.weight write errors disappear from logcat.
Change-Id: Idbfb49c25afec12b21daea7a17db5322bc981ff0
Signed-off-by: Bart Van Assche <bvanassche@google.com>

libprocessgroup/profiles/cgroups.json

diff --git a/libprocessgroup/profiles/cgroups.json b/libprocessgroup/profiles/cgroups.json
index 1c833d8..3e4393d 100644
--- a/libprocessgroup/profiles/cgroups.json
+++ b/libprocessgroup/profiles/cgroups.json
@@ -3,7 +3,7 @@
     {
       "Controller": "blkio",
       "Path": "/dev/blkio",
-      "Mode": "0755",
+      "Mode": "0775",
       "UID": "system",
       "GID": "system"
     },
@@ -32,7 +32,7 @@
   ],
   "Cgroups2": {
     "Path": "/sys/fs/cgroup",
-    "Mode": "0755",
+    "Mode": "0775",
     "UID": "system",
     "GID": "system",
     "Controllers": [