@@ -487,8 +487,16 @@ start_thread (void *arg)
/* This prevents sending a signal from this thread to itself during
its final stages. This must come after the exit call above
- because atexit handlers must not run with signals blocked. */
- __libc_signal_block_all (NULL);
+ because atexit handlers must not run with signals blocked.
+
+ Do not block SIGSETXID. The setxid handshake below expects the
+ signal to be delivered. (SIGSETXID cannot run application code,
+ nor does it use pthread_kill.) Reuse the pd->sigmask space for
+ computing the signal mask, to save stack space. */
+ memset (&pd->sigmask, -1, sizeof (pd->sigmask));
+ __sigdelset (&pd->sigmask, SIGSETXID);
+ INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_BLOCK, &pd->sigmask, NULL,
+ __NSIG_BYTES);
/* Tell __pthread_kill_internal that this thread is about to exit.
If there is a __pthread_kill_internal in progress, this delays
@@ -118,6 +118,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \
tst-unload \
tst-unwind-thread \
tst-pt-vfork1 tst-pt-vfork2 tst-vfork1x tst-vfork2x \
+ tst-pthread-setuid-loop \
tst-pthread_cancel-exited \
tst-pthread_cancel-select-loop \
tst-pthread_kill-exited \
new file mode 100644
@@ -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>