v4.19.13 snapshot.
diff --git a/kernel/uid16.c b/kernel/uid16.c
new file mode 100644
index 0000000..af6925d
--- /dev/null
+++ b/kernel/uid16.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Wrapper functions for 16bit uid back compatibility. All nicely tied
+ * together in the faint hope we can take the out in five years time.
+ */
+
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/notifier.h>
+#include <linux/reboot.h>
+#include <linux/prctl.h>
+#include <linux/capability.h>
+#include <linux/init.h>
+#include <linux/highuid.h>
+#include <linux/security.h>
+#include <linux/cred.h>
+#include <linux/syscalls.h>
+
+#include <linux/uaccess.h>
+
+#include "uid16.h"
+
+SYSCALL_DEFINE3(chown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
+{
+ return ksys_chown(filename, low2highuid(user), low2highgid(group));
+}
+
+SYSCALL_DEFINE3(lchown16, const char __user *, filename, old_uid_t, user, old_gid_t, group)
+{
+ return ksys_lchown(filename, low2highuid(user), low2highgid(group));
+}
+
+SYSCALL_DEFINE3(fchown16, unsigned int, fd, old_uid_t, user, old_gid_t, group)
+{
+ return ksys_fchown(fd, low2highuid(user), low2highgid(group));
+}
+
+SYSCALL_DEFINE2(setregid16, old_gid_t, rgid, old_gid_t, egid)
+{
+ return __sys_setregid(low2highgid(rgid), low2highgid(egid));
+}
+
+SYSCALL_DEFINE1(setgid16, old_gid_t, gid)
+{
+ return __sys_setgid(low2highgid(gid));
+}
+
+SYSCALL_DEFINE2(setreuid16, old_uid_t, ruid, old_uid_t, euid)
+{
+ return __sys_setreuid(low2highuid(ruid), low2highuid(euid));
+}
+
+SYSCALL_DEFINE1(setuid16, old_uid_t, uid)
+{
+ return __sys_setuid(low2highuid(uid));
+}
+
+SYSCALL_DEFINE3(setresuid16, old_uid_t, ruid, old_uid_t, euid, old_uid_t, suid)
+{
+ return __sys_setresuid(low2highuid(ruid), low2highuid(euid),
+ low2highuid(suid));
+}
+
+SYSCALL_DEFINE3(getresuid16, old_uid_t __user *, ruidp, old_uid_t __user *, euidp, old_uid_t __user *, suidp)
+{
+ const struct cred *cred = current_cred();
+ int retval;
+ old_uid_t ruid, euid, suid;
+
+ ruid = high2lowuid(from_kuid_munged(cred->user_ns, cred->uid));
+ euid = high2lowuid(from_kuid_munged(cred->user_ns, cred->euid));
+ suid = high2lowuid(from_kuid_munged(cred->user_ns, cred->suid));
+
+ if (!(retval = put_user(ruid, ruidp)) &&
+ !(retval = put_user(euid, euidp)))
+ retval = put_user(suid, suidp);
+
+ return retval;
+}
+
+SYSCALL_DEFINE3(setresgid16, old_gid_t, rgid, old_gid_t, egid, old_gid_t, sgid)
+{
+ return __sys_setresgid(low2highgid(rgid), low2highgid(egid),
+ low2highgid(sgid));
+}
+
+SYSCALL_DEFINE3(getresgid16, old_gid_t __user *, rgidp, old_gid_t __user *, egidp, old_gid_t __user *, sgidp)
+{
+ const struct cred *cred = current_cred();
+ int retval;
+ old_gid_t rgid, egid, sgid;
+
+ rgid = high2lowgid(from_kgid_munged(cred->user_ns, cred->gid));
+ egid = high2lowgid(from_kgid_munged(cred->user_ns, cred->egid));
+ sgid = high2lowgid(from_kgid_munged(cred->user_ns, cred->sgid));
+
+ if (!(retval = put_user(rgid, rgidp)) &&
+ !(retval = put_user(egid, egidp)))
+ retval = put_user(sgid, sgidp);
+
+ return retval;
+}
+
+SYSCALL_DEFINE1(setfsuid16, old_uid_t, uid)
+{
+ return __sys_setfsuid(low2highuid(uid));
+}
+
+SYSCALL_DEFINE1(setfsgid16, old_gid_t, gid)
+{
+ return __sys_setfsgid(low2highgid(gid));
+}
+
+static int groups16_to_user(old_gid_t __user *grouplist,
+ struct group_info *group_info)
+{
+ struct user_namespace *user_ns = current_user_ns();
+ int i;
+ old_gid_t group;
+ kgid_t kgid;
+
+ for (i = 0; i < group_info->ngroups; i++) {
+ kgid = group_info->gid[i];
+ group = high2lowgid(from_kgid_munged(user_ns, kgid));
+ if (put_user(group, grouplist+i))
+ return -EFAULT;
+ }
+
+ return 0;
+}
+
+static int groups16_from_user(struct group_info *group_info,
+ old_gid_t __user *grouplist)
+{
+ struct user_namespace *user_ns = current_user_ns();
+ int i;
+ old_gid_t group;
+ kgid_t kgid;
+
+ for (i = 0; i < group_info->ngroups; i++) {
+ if (get_user(group, grouplist+i))
+ return -EFAULT;
+
+ kgid = make_kgid(user_ns, low2highgid(group));
+ if (!gid_valid(kgid))
+ return -EINVAL;
+
+ group_info->gid[i] = kgid;
+ }
+
+ return 0;
+}
+
+SYSCALL_DEFINE2(getgroups16, int, gidsetsize, old_gid_t __user *, grouplist)
+{
+ const struct cred *cred = current_cred();
+ int i;
+
+ if (gidsetsize < 0)
+ return -EINVAL;
+
+ i = cred->group_info->ngroups;
+ if (gidsetsize) {
+ if (i > gidsetsize) {
+ i = -EINVAL;
+ goto out;
+ }
+ if (groups16_to_user(grouplist, cred->group_info)) {
+ i = -EFAULT;
+ goto out;
+ }
+ }
+out:
+ return i;
+}
+
+SYSCALL_DEFINE2(setgroups16, int, gidsetsize, old_gid_t __user *, grouplist)
+{
+ struct group_info *group_info;
+ int retval;
+
+ if (!may_setgroups())
+ return -EPERM;
+ if ((unsigned)gidsetsize > NGROUPS_MAX)
+ return -EINVAL;
+
+ group_info = groups_alloc(gidsetsize);
+ if (!group_info)
+ return -ENOMEM;
+ retval = groups16_from_user(group_info, grouplist);
+ if (retval) {
+ put_group_info(group_info);
+ return retval;
+ }
+
+ groups_sort(group_info);
+ retval = set_current_groups(group_info);
+ put_group_info(group_info);
+
+ return retval;
+}
+
+SYSCALL_DEFINE0(getuid16)
+{
+ return high2lowuid(from_kuid_munged(current_user_ns(), current_uid()));
+}
+
+SYSCALL_DEFINE0(geteuid16)
+{
+ return high2lowuid(from_kuid_munged(current_user_ns(), current_euid()));
+}
+
+SYSCALL_DEFINE0(getgid16)
+{
+ return high2lowgid(from_kgid_munged(current_user_ns(), current_gid()));
+}
+
+SYSCALL_DEFINE0(getegid16)
+{
+ return high2lowgid(from_kgid_munged(current_user_ns(), current_egid()));
+}