commit 2a6b8307fa4243a7921270aedf8ce6506e31569a
Author: Steve Dickson <steved@redhat.com>
Date:   Tue Jul 17 15:09:37 2018 -0400

    rpc.gssd: truncates 32-bit UIDs/GIDs to 16 bits architectures.
    
    utils/gssd_proc.c uses SYS_setresuid and SYS_setresgid in
    change_identity when it should use SYS_setresuid32 and
    SYS_setresgid32 instead. This causes it to truncate
    UIDs/GIDs > 65536.
    
    Fixes: https://bugs.launchpad.net/ubuntu/+source/nfs-utils/+bug/1779962
    Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1595927
    
    Tested-by: James Ettle <theholyettlz@googlemail.com>
    Tested-by: Sree <Sree@gmail.com>
    Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c
index 8767e26..7a57c4e 100644
--- a/utils/gssd/gssd_proc.c
+++ b/utils/gssd/gssd_proc.c
@@ -434,6 +434,7 @@ static int
 change_identity(uid_t uid)
 {
 	struct passwd	*pw;
+	int res;
 
 	/* drop list of supplimentary groups first */
 	if (syscall(SYS_setgroups, 0, 0) != 0) {
@@ -459,14 +460,23 @@ change_identity(uid_t uid)
 	 * send a signal to all other threads to synchronize the uid in all
 	 * other threads. To bypass this, we have to call syscall() directly.
 	 */
-	if (syscall(SYS_setresgid, pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) {
+#ifdef __NR_setresuid32
+	res = syscall(SYS_setresgid32, pw->pw_gid, pw->pw_gid, pw->pw_gid);
+#else 
+	res = syscall(SYS_setresgid, pw->pw_gid, pw->pw_gid, pw->pw_gid);
+#endif
+	if (res != 0) {
 		printerr(0, "WARNING: failed to set gid to %u!\n", pw->pw_gid);
 		return errno;
 	}
 
-	if (syscall(SYS_setresuid, uid, uid, uid) != 0) {
-		printerr(0, "WARNING: Failed to setuid for user with uid %u\n",
-				uid);
+#ifdef __NR_setresuid32
+	res = syscall(SYS_setresuid32, uid, uid, uid);
+#else 
+	res = syscall(SYS_setresuid, uid, uid, uid);
+#endif
+	if (res != 0) {
+		printerr(0, "WARNING: Failed to setuid for user with uid %u\n", uid);
 		return errno;
 	}