1 files changed, 61 insertions, 0 deletions
diff --git a/sysdeps/pthread/tst-pthread-setuid-loop.c b/sysdeps/pthread/tst-pthread-setuid-loop.c
new file mode 100644
index 0000000000..fda2a49b7f
--- /dev/null
+++ b/sysdeps/pthread/tst-pthread-setuid-loop.c
@@ -0,0 +1,61 @@
+/* Test that setuid, pthread_create, thread exit do not deadlock (bug 28361).
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xthread.h>
+#include <unistd.h>
+
+/* How many threads to launch during each iteration.  */
+enum { threads = 4 };
+
+/* How many iterations to perform.  This value seems to reproduce
+   bug 28361 in a bout one in three runs.  */
+enum { iterations = 5000 };
+
+/* Cache of the real user ID used by setuid_thread.  */
+static uid_t uid;
+
+/* Start routine for the threads.  */
+static void *
+setuid_thread (void *closure)
+{
+  TEST_COMPARE (setuid (uid), 0);
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  /* The setxid machinery is still invoked even if the UID is
+     unchanged.  (The kernel might reset other credentials as part of
+     the system call.)  */
+  uid = getuid ();
+
+  for (int i = 0; i < iterations; ++i)
+    {
+      pthread_t thread_ids[threads];
+      for (int j = 0; j < threads; ++j)
+        thread_ids[j] = xpthread_create (NULL, setuid_thread, NULL);
+      for (int j = 0; j < threads; ++j)
+        xpthread_join (thread_ids[j]);
+    }
+
+  return 0;
+}
+
+#include <support/test-driver.c>