diff --git a/libcutils/Android.bp b/libcutils/Android.bp
index cfe8d29..f483308 100644
--- a/libcutils/Android.bp
+++ b/libcutils/Android.bp
@@ -112,7 +112,7 @@
                 "properties.cpp",
                 "qtaguid.c",
                 "trace-dev.c",
-                "uevent.c",
+                "uevent.cpp",
             ],
             sanitize: {
                 misc_undefined: ["integer"],
diff --git a/libcutils/include/private/android_filesystem_config.h b/libcutils/include/private/android_filesystem_config.h
index 55ece54..2ecf5bc 100644
--- a/libcutils/include/private/android_filesystem_config.h
+++ b/libcutils/include/private/android_filesystem_config.h
@@ -170,6 +170,14 @@
 #define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
 #define AID_SHARED_GID_END 59999   /* end of gids for apps in each user to share */
 
+/*
+ * This is a magic number in the kernel and not something that was picked
+ * arbitrarily. This value is returned whenever a uid that has no mapping in the
+ * user namespace is returned to userspace:
+ * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/highuid.h?h=v4.4#n40
+ */
+#define AID_OVERFLOWUID 65534 /* unmapped user in the user namespace */
+
 #define AID_ISOLATED_START 99000 /* start of uids for fully isolated sandboxed processes */
 #define AID_ISOLATED_END 99999   /* end of uids for fully isolated sandboxed processes */
 
diff --git a/libcutils/uevent.c b/libcutils/uevent.c
deleted file mode 100644
index f548dca..0000000
--- a/libcutils/uevent.c
+++ /dev/null
@@ -1,133 +0,0 @@
-/*
- * Copyright (C) 2011 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <cutils/uevent.h>
-
-#include <errno.h>
-#include <stdbool.h>
-#include <string.h>
-#include <strings.h>
-#include <sys/socket.h>
-#include <sys/un.h>
-#include <unistd.h>
-
-#include <linux/netlink.h>
-
-/**
- * Like recv(), but checks that messages actually originate from the kernel.
- */
-ssize_t uevent_kernel_multicast_recv(int socket, void *buffer, size_t length)
-{
-    uid_t uid = -1;
-    return uevent_kernel_multicast_uid_recv(socket, buffer, length, &uid);
-}
-
-/**
- * Like the above, but passes a uid_t in by pointer. In the event that this
- * fails due to a bad uid check, the uid_t will be set to the uid of the
- * socket's peer.
- *
- * If this method rejects a netlink message from outside the kernel, it
- * returns -1, sets errno to EIO, and sets "user" to the UID associated with the
- * message. If the peer UID cannot be determined, "user" is set to -1."
- */
-ssize_t uevent_kernel_multicast_uid_recv(int socket, void *buffer, size_t length, uid_t *uid)
-{
-    return uevent_kernel_recv(socket, buffer, length, true, uid);
-}
-
-ssize_t uevent_kernel_recv(int socket, void *buffer, size_t length, bool require_group, uid_t *uid)
-{
-    struct iovec iov = { buffer, length };
-    struct sockaddr_nl addr;
-    char control[CMSG_SPACE(sizeof(struct ucred))];
-    struct msghdr hdr = {
-        &addr,
-        sizeof(addr),
-        &iov,
-        1,
-        control,
-        sizeof(control),
-        0,
-    };
-
-    *uid = -1;
-    ssize_t n = recvmsg(socket, &hdr, 0);
-    if (n <= 0) {
-        return n;
-    }
-
-    struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
-    if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
-        /* ignoring netlink message with no sender credentials */
-        goto out;
-    }
-
-    struct ucred *cred = (struct ucred *)CMSG_DATA(cmsg);
-    *uid = cred->uid;
-    if (cred->uid != 0) {
-        /* ignoring netlink message from non-root user */
-        goto out;
-    }
-
-    if (addr.nl_pid != 0) {
-        /* ignore non-kernel */
-        goto out;
-    }
-    if (require_group && addr.nl_groups == 0) {
-        /* ignore unicast messages when requested */
-        goto out;
-    }
-
-    return n;
-
-out:
-    /* clear residual potentially malicious data */
-    bzero(buffer, length);
-    errno = EIO;
-    return -1;
-}
-
-int uevent_open_socket(int buf_sz, bool passcred)
-{
-    struct sockaddr_nl addr;
-    int on = passcred;
-    int s;
-
-    memset(&addr, 0, sizeof(addr));
-    addr.nl_family = AF_NETLINK;
-    addr.nl_pid = getpid();
-    addr.nl_groups = 0xffffffff;
-
-    s = socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT);
-    if(s < 0)
-        return -1;
-
-    /* buf_sz should be less than net.core.rmem_max for this to succeed */
-    if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, &buf_sz, sizeof(buf_sz)) < 0) {
-        close(s);
-        return -1;
-    }
-
-    setsockopt(s, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
-
-    if(bind(s, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
-        close(s);
-        return -1;
-    }
-
-    return s;
-}
diff --git a/libcutils/uevent.cpp b/libcutils/uevent.cpp
new file mode 100644
index 0000000..a84e5b0
--- /dev/null
+++ b/libcutils/uevent.cpp
@@ -0,0 +1,177 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cutils/uevent.h>
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+#include <strings.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include <linux/netlink.h>
+
+#include <fstream>
+
+#include <private/android_filesystem_config.h>
+
+namespace {
+
+// Returns the uid of root in the current user namespace.
+// Returns AID_OVERFLOWUID if the root user is not mapped in the current
+// namespace.
+// Returns 0 if the kernel is not user namespace-aware (for backwards
+// compatibility) or if AID_OVERFLOWUID could not be validated to match what the
+// kernel would return.
+uid_t GetRootUid() {
+    constexpr uid_t kParentRootUid = 0;
+
+    std::ifstream uid_map_file("/proc/self/uid_map");
+    if (!uid_map_file) {
+        // The kernel does not support user namespaces.
+        return kParentRootUid;
+    }
+
+    uid_t current_namespace_uid, parent_namespace_uid;
+    uint32_t length;
+    while (uid_map_file >> current_namespace_uid >> parent_namespace_uid >> length) {
+        // Since kParentRootUid is 0, it should be the first entry in the mapped
+        // range.
+        if (parent_namespace_uid != kParentRootUid || length < 1) continue;
+        return current_namespace_uid;
+    }
+
+    // Sanity check: verify that the overflow UID is the one to be returned by
+    // the kernel.
+    std::ifstream overflowuid_file("/proc/sys/kernel/overflowuid");
+    if (!overflowuid_file) {
+        // It's better to return 0 in case we cannot make sure that the overflow
+        // UID matches.
+        return kParentRootUid;
+    }
+    uid_t kernel_overflow_uid;
+    if (!(overflowuid_file >> kernel_overflow_uid) || kernel_overflow_uid != AID_OVERFLOWUID)
+        return kParentRootUid;
+
+    // root is unmapped, use the kernel "overflow" uid.
+    return AID_OVERFLOWUID;
+}
+
+}  // namespace
+
+extern "C" {
+
+/**
+ * Like recv(), but checks that messages actually originate from the kernel.
+ */
+ssize_t uevent_kernel_multicast_recv(int socket, void* buffer, size_t length) {
+    uid_t uid = -1;
+    return uevent_kernel_multicast_uid_recv(socket, buffer, length, &uid);
+}
+
+/**
+ * Like the above, but passes a uid_t in by pointer. In the event that this
+ * fails due to a bad uid check, the uid_t will be set to the uid of the
+ * socket's peer.
+ *
+ * If this method rejects a netlink message from outside the kernel, it
+ * returns -1, sets errno to EIO, and sets "user" to the UID associated with the
+ * message. If the peer UID cannot be determined, "user" is set to -1."
+ */
+ssize_t uevent_kernel_multicast_uid_recv(int socket, void* buffer, size_t length, uid_t* uid) {
+    return uevent_kernel_recv(socket, buffer, length, true, uid);
+}
+
+ssize_t uevent_kernel_recv(int socket, void* buffer, size_t length, bool require_group, uid_t* uid) {
+    static const uid_t root_uid = GetRootUid();
+    struct iovec iov = {buffer, length};
+    struct sockaddr_nl addr;
+    char control[CMSG_SPACE(sizeof(struct ucred))];
+    struct msghdr hdr = {
+        &addr, sizeof(addr), &iov, 1, control, sizeof(control), 0,
+    };
+    struct ucred* cred;
+
+    *uid = -1;
+    ssize_t n = recvmsg(socket, &hdr, 0);
+    if (n <= 0) {
+        return n;
+    }
+
+    struct cmsghdr* cmsg = CMSG_FIRSTHDR(&hdr);
+    if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
+        /* ignoring netlink message with no sender credentials */
+        goto out;
+    }
+
+    cred = (struct ucred*)CMSG_DATA(cmsg);
+    *uid = cred->uid;
+    if (cred->uid != root_uid) {
+        /* ignoring netlink message from non-root user */
+        goto out;
+    }
+
+    if (addr.nl_pid != 0) {
+        /* ignore non-kernel */
+        goto out;
+    }
+    if (require_group && addr.nl_groups == 0) {
+        /* ignore unicast messages when requested */
+        goto out;
+    }
+
+    return n;
+
+out:
+    /* clear residual potentially malicious data */
+    bzero(buffer, length);
+    errno = EIO;
+    return -1;
+}
+
+int uevent_open_socket(int buf_sz, bool passcred) {
+    struct sockaddr_nl addr;
+    int on = passcred;
+    int s;
+
+    memset(&addr, 0, sizeof(addr));
+    addr.nl_family = AF_NETLINK;
+    addr.nl_pid = getpid();
+    addr.nl_groups = 0xffffffff;
+
+    s = socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT);
+    if (s < 0) return -1;
+
+    /* buf_sz should be less than net.core.rmem_max for this to succeed */
+    if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, &buf_sz, sizeof(buf_sz)) < 0) {
+        close(s);
+        return -1;
+    }
+
+    setsockopt(s, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
+
+    if (bind(s, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
+        close(s);
+        return -1;
+    }
+
+    return s;
+}
+
+}  // extern "C"