glibc/pthread-kill-fail-after-exit.patch

From 3abf3bd4edc86fb28c099cc85203cb46a811e0b8 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Mon, 13 Sep 2021 11:06:08 +0200
Subject: [PATCH] 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)
---
 NEWS                                        |  1 +
 nptl/pthread_cancel.c                       |  9 ++-
 nptl/pthread_kill.c                         |  7 +-
 sysdeps/pthread/Makefile                    |  5 +-
 sysdeps/pthread/tst-kill4.c                 | 90 ---------------------
 sysdeps/pthread/tst-pthread_cancel-exited.c | 45 +++++++++++
 sysdeps/pthread/tst-pthread_kill-exited.c   | 46 +++++++++++
 7 files changed, 107 insertions(+), 96 deletions(-)
 delete mode 100644 sysdeps/pthread/tst-kill4.c
 create mode 100644 sysdeps/pthread/tst-pthread_cancel-exited.c
 create mode 100644 sysdeps/pthread/tst-pthread_kill-exited.c

diff --git a/nptl/pthread_cancel.c b/nptl/pthread_cancel.c
index cc25ff21f3..9bac6e3b76 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 f79a2b26fc..5d4c86f920 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 42f9fc5072..dedfa0d290 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 \
diff --git a/sysdeps/pthread/tst-kill4.c b/sysdeps/pthread/tst-kill4.c
deleted file mode 100644
index 9563939792..0000000000
--- 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"