logd: allow logd to write to /dev/cpuset files

Required by logd on devices with USE_CPUSETS defined.

Make /dev/cpuset/background, /dev/cpuset/foreground and
/dev/cpuset/task writeable by system gid. Add logd to system
group for writing to cpuset files and to root group to avoid
regressions. When dropping privs, also drop supplementary groups.

Bug: 22699101
Change-Id: Icc01769b18b5e1f1649623da8325a8bfabc3a3f0

1 files changed, 4 insertions, 0 deletions

diff --git a/logd/main.cpp b/logd/main.cpp
index 9b88983..a3241d0 100644
--- a/logd/main.cpp
+++ b/logd/main.cpp
@@ -103,6 +103,10 @@ static int drop_privs() {
         return -1;
     }
 
+    if (setgroups(0, NULL) == -1) {
+        return -1;
+    }
+
     if (setgid(AID_LOGD) != 0) {
         return -1;
     }