From f8825fafc810e831cccd3a8ad61c064f55d4fa45 Mon Sep 17 00:00:00 2001
From: David Anderson <dvander@google.com>
Date: Fri, 2 Jul 2021 20:47:27 -0700
Subject: [PATCH] Fix gid not being set in ueventd when device nodes already
 exist.

The chown() call will fix the uid for pre-existing nodes, but not the
gid. This fix ensures the correct gid is set if needed.

Bug: 187738549
Test: manual test modifying ueventd.rc
Change-Id: I0fadd745a7c57a089fed9afc2572ace597a05396
---
 init/devices.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/init/devices.cpp b/init/devices.cpp
index ce6298a9d..56c66239e 100644
--- a/init/devices.cpp
+++ b/init/devices.cpp
@@ -264,6 +264,8 @@ void DeviceHandler::MakeDevice(const std::string& path, bool block, int major, i
         setfscreatecon(secontext.c_str());
     }
 
+    gid_t new_group = -1;
+
     dev_t dev = makedev(major, minor);
     /* Temporarily change egid to avoid race condition setting the gid of the
      * device node. Unforunately changing the euid would prevent creation of
@@ -291,10 +293,21 @@ void DeviceHandler::MakeDevice(const std::string& path, bool block, int major, i
             PLOG(ERROR) << "Cannot set '" << secontext << "' SELinux label on '" << path
                         << "' device";
         }
+
+        struct stat s;
+        if (stat(path.c_str(), &s) == 0) {
+            if (gid != s.st_gid) {
+                new_group = gid;
+            }
+        } else {
+            PLOG(ERROR) << "Cannot stat " << path;
+        }
     }
 
 out:
-    chown(path.c_str(), uid, -1);
+    if (chown(path.c_str(), uid, new_group) < 0) {
+        PLOG(ERROR) << "Cannot chown " << path << " " << uid << " " << new_group;
+    }
     if (setegid(AID_ROOT)) {
         PLOG(FATAL) << "setegid(AID_ROOT) failed";
     }