1 files changed, 21 insertions, 2 deletions

diff --git a/libbb/change_identity.c b/libbb/change_identity.c
index 619db09a8..d48d86326 100644
--- a/libbb/change_identity.c
+++ b/libbb/change_identity.c
@@ -33,9 +33,28 @@
 /* Become the user and group(s) specified by PW.  */
 void FAST_FUNC change_identity(const struct passwd *pw)
 {
-        if (initgroups(pw->pw_name, pw->pw_gid) == -1)
-                bb_perror_msg_and_die("can't set groups");
+        int res;
+
+        res = initgroups(pw->pw_name, pw->pw_gid);
         endgrent(); /* helps to close a fd used internally by libc */
+
+        if (res != 0) {
+                /*
+                 * If initgroups() fails because a system call is unimplemented
+                 * then we are running on a Linux kernel compiled without multiuser
+                 * support (CONFIG_MULTIUSER is not defined).
+                 *
+                 * If we are running without multiuser support *and* the target uid
+                 * already matches the current uid then we can skip the change of
+                 * identity.
+                 */
+                if (errno == ENOSYS && pw->pw_uid == getuid()) {
+                        return;
+                }
+
+                bb_perror_msg_and_die("can't set groups");
+        }
+
         xsetgid(pw->pw_gid);
         xsetuid(pw->pw_uid);
 }