commit 3abf3bd4edc86fb28c099cc85203cb46a811e0b8

Author: Florian Weimer <fweimer@redhat.com>

Date:   Mon Sep 13 11:06:08 2021 +0200

    nptl: pthread_kill, pthread_cancel should not fail after exit (bug 19193)

    This closes one remaining race condition related to bug 12889: if

    the thread already exited on the kernel side, returning ESRCH

    is not correct because that error is reserved for the thread IDs

    (pthread_t values) whose lifetime has ended.  In case of a

    kernel-side exit and a valid thread ID, no signal needs to be sent

    and cancellation does not have an effect, so just return 0.

    sysdeps/pthread/tst-kill4.c triggers undefined behavior and is

    removed with this commit.

    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

    (cherry picked from commit 8af8456004edbab71f8903a60a3cae442cf6fe69)

diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c

index cc25ff21f364e8a4..9bac6e3b76a20312 100644

--- a/nptl/pthread_cancel.c

+++ b/nptl/pthread_cancel.c

@@ -62,10 +62,11 @@ __pthread_cancel (pthread_t th)

 {

   volatile struct pthread *pd = (volatile struct pthread *) th;

-  /* Make sure the descriptor is valid.  */

-  if (INVALID_TD_P (pd))

-    /* Not a valid thread handle.  */

-    return ESRCH;

+  if (pd->tid == 0)

+    /* The thread has already exited on the kernel side.  Its outcome

+       (regular exit, other cancelation) has already been

+       determined.  */

+    return 0;

   static int init_sigcancel = 0;

   if (atomic_load_relaxed (&init_sigcancel) == 0)

diff --git a/nptl/pthread_kill.c b/nptl/pthread_kill.c

index f79a2b26fc7f72e5..5d4c86f9205a6fb5 100644

--- a/nptl/pthread_kill.c

+++ b/nptl/pthread_kill.c

@@ -46,7 +46,12 @@ __pthread_kill_internal (pthread_t threadid, int signo)

 	    ? INTERNAL_SYSCALL_ERRNO (val) : 0);

     }

   else

-    val = ESRCH;

+    /* The kernel reports that the thread has exited.  POSIX specifies

+       the ESRCH error only for the case when the lifetime of a thread

+       ID has ended, but calling pthread_kill on such a thread ID is

+       undefined in glibc.  Therefore, do not treat kernel thread exit

+       as an error.  */

+    val = 0;

   return val;

 }

diff --git a/sysdeps/pthread/Makefile b/sysdeps/pthread/Makefile

index 42f9fc507263657d..dedfa0d290da4949 100644

--- a/sysdeps/pthread/Makefile

+++ b/sysdeps/pthread/Makefile

@@ -89,7 +89,7 @@ tests += tst-cnd-basic tst-mtx-trylock tst-cnd-broadcast \

 	 tst-join8 tst-join9 tst-join10 tst-join11 tst-join12 tst-join13 \

 	 tst-join14 tst-join15 \

 	 tst-key1 tst-key2 tst-key3 tst-key4 \

-	 tst-kill1 tst-kill2 tst-kill3 tst-kill4 tst-kill5 tst-kill6 \

+	 tst-kill1 tst-kill2 tst-kill3 tst-kill5 tst-kill6 \

 	 tst-locale1 tst-locale2 \

 	 tst-memstream \

 	 tst-mutex-errorcheck tst-mutex1 tst-mutex2 tst-mutex3 tst-mutex4 \

@@ -118,6 +118,9 @@ 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_cancel-exited \

+	 tst-pthread_kill-exited \

+	 # tests

 tests-time64 := \

   tst-abstime-time64 \

diff --git a/sysdeps/pthread/tst-kill4.c b/sysdeps/pthread/tst-kill4.c

deleted file mode 100644

index 9563939792b96ebd..0000000000000000

--- a/sysdeps/pthread/tst-kill4.c

+++ /dev/null

@@ -1,90 +0,0 @@

-/* Copyright (C) 2003-2021 Free Software Foundation, Inc.

-   This file is part of the GNU C Library.

-   Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.

-

-   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 <errno.h>

-#include <pthread.h>

-#include <signal.h>

-#include <stdio.h>

-#include <stdlib.h>

-#include <unistd.h>

-

-

-static void *

-tf (void *a)

-{

-  return NULL;

-}

-

-

-int

-do_test (void)

-{

-  pthread_attr_t at;

-  if (pthread_attr_init (&at) != 0)

-    {

-      puts ("attr_create failed");

-      exit (1);

-    }

-

-  /* Limit thread stack size, because if it is too large, pthread_join

-     will free it immediately rather than put it into stack cache.  */

-  if (pthread_attr_setstacksize (&at, 2 * 1024 * 1024) != 0)

-    {

-      puts ("setstacksize failed");

-      exit (1);

-    }

-

-  pthread_t th;

-  if (pthread_create (&th, &at, tf, NULL) != 0)

-    {

-      puts ("create failed");

-      exit (1);

-    }

-

-  pthread_attr_destroy (&at);

-

-  if (pthread_join (th, NULL) != 0)

-    {

-      puts ("join failed");

-      exit (1);

-    }

-

-  /* The following only works because we assume here something about

-     the implementation.  Namely, that the memory allocated for the

-     thread descriptor is not going away, that the TID field is

-     cleared and therefore the signal is sent to process 0, and that

-     we can savely assume there is no other process with this ID at

-     that time.  */

-  int e = pthread_kill (th, 0);

-  if (e == 0)

-    {

-      puts ("pthread_kill succeeded");

-      exit (1);

-    }

-  if (e != ESRCH)

-    {

-      puts ("pthread_kill didn't return ESRCH");

-      exit (1);

-    }

-

-  return 0;

-}

-

-

-#define TEST_FUNCTION do_test ()

-#include "../test-skeleton.c"

diff --git a/sysdeps/pthread/tst-pthread_cancel-exited.c b/sysdeps/pthread/tst-pthread_cancel-exited.c

new file mode 100644

index 0000000000000000..811c9bee07ab2638

--- /dev/null

+++ b/sysdeps/pthread/tst-pthread_cancel-exited.c

@@ -0,0 +1,45 @@

+/* Test that pthread_kill succeeds for an exited thread.

+   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/>.  */

+

+/* This test verifies that pthread_kill returns 0 (and not ESRCH) for

+   a thread that has exited on the kernel side.  */

+

+#include <stddef.h>

+#include <support/support.h>

+#include <support/xthread.h>

+

+static void *

+noop_thread (void *closure)

+{

+  return NULL;

+}

+

+static int

+do_test (void)

+{

+  pthread_t thr = xpthread_create (NULL, noop_thread, NULL);

+

+  support_wait_for_thread_exit ();

+

+  xpthread_cancel (thr);

+  xpthread_join (thr);

+

+  return 0;

+}

+

+#include <support/test-driver.c>

diff --git a/sysdeps/pthread/tst-pthread_kill-exited.c b/sysdeps/pthread/tst-pthread_kill-exited.c

new file mode 100644

index 0000000000000000..7575fb6d58cae99c

--- /dev/null

+++ b/sysdeps/pthread/tst-pthread_kill-exited.c

@@ -0,0 +1,46 @@

+/* Test that pthread_kill succeeds for an exited thread.

+   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/>.  */

+

+/* This test verifies that pthread_kill returns 0 (and not ESRCH) for

+   a thread that has exited on the kernel side.  */

+

+#include <signal.h>

+#include <stddef.h>

+#include <support/support.h>

+#include <support/xthread.h>

+

+static void *

+noop_thread (void *closure)

+{

+  return NULL;

+}

+

+static int

+do_test (void)

+{

+  pthread_t thr = xpthread_create (NULL, noop_thread, NULL);

+

+  support_wait_for_thread_exit ();

+

+  xpthread_kill (thr, SIGUSR1);

+  xpthread_join (thr);

+

+  return 0;

+}

+

+#include <support/test-driver.c>