From fe2c818f75d8f9b7b4bebb411f2970fda4f2fcb6 Mon Sep 17 00:00:00 2001
From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon, 23 Aug 2021 14:30:51 -0300
Subject: [PATCH] nptl: Use exit_lock when accessing TID on pthread_getname_np

Also return EINVAL if the thread is already terminated at the time
of the call.

Checked on x86_64-linux-gnu.
---
 nptl/pthread_getname.c               | 65 +++++++++++++++++-----------
 sysdeps/pthread/tst-pthread-exited.c |  6 +++
 2 files changed, 45 insertions(+), 26 deletions(-)

diff --git a/nptl/pthread_getname.c b/nptl/pthread_getname.c
index 535932b815..ac9f4ad089 100644
--- a/nptl/pthread_getname.c
+++ b/nptl/pthread_getname.c
@@ -16,43 +16,27 @@
    License along with the GNU C Library; see the file COPYING.LIB.  If
    not, see <https://www.gnu.org/licenses/>.  */
 
-#include <errno.h>
-#include <fcntl.h>
+#include <intprops.h>
+#include <libc-lock.h>
+#include <not-cancel.h>
 #include <pthreadP.h>
+#include <shlib-compat.h>
 #include <stdio.h>
-#include <string.h>
-#include <unistd.h>
 #include <sys/prctl.h>
-#include <not-cancel.h>
-#include <shlib-compat.h>
 
-int
-__pthread_getname_np (pthread_t th, char *buf, size_t len)
+static int
+getname (pid_t tid, char *buf, size_t len)
 {
-  const struct pthread *pd = (const struct pthread *) th;
-
-  /* Unfortunately the kernel headers do not export the TASK_COMM_LEN
-     macro.  So we have to define it here.  */
-#define TASK_COMM_LEN 16
-  if (len < TASK_COMM_LEN)
-    return ERANGE;
-
-  if (pd == THREAD_SELF)
-    return __prctl (PR_GET_NAME, buf) ? errno : 0;
-
-#define FMT "/proc/self/task/%u/comm"
-  char fname[sizeof (FMT) + 8];
-  sprintf (fname, FMT, (unsigned int) pd->tid);
+  char fname[sizeof ("/proc/self/task//comm") + INT_BUFSIZE_BOUND (pid_t)];
+  __snprintf (fname, sizeof (fname), "/proc/self/task/%d/comm", tid);
 
   int fd = __open64_nocancel (fname, O_RDONLY);
   if (fd == -1)
-    return errno;
+    return EINVAL;
 
   int res = 0;
   ssize_t n = TEMP_FAILURE_RETRY (__read_nocancel (fd, buf, len));
-  if (n < 0)
-    res = errno;
-  else
+  if (n > 0)
     {
       if (buf[n - 1] == '\n')
 	buf[n - 1] = '\0';
@@ -61,11 +45,40 @@ __pthread_getname_np (pthread_t th, char *buf, size_t len)
       else
 	buf[n] = '\0';
     }
+  else
+    res = errno == ENOENT ? EINVAL : errno;;
 
   __close_nocancel_nostatus (fd);
 
   return res;
 }
+
+int
+__pthread_getname_np (pthread_t th, char *buf, size_t len)
+{
+  struct pthread *pd = (struct pthread *) th;
+
+  /* Unfortunately the kernel headers do not export the TASK_COMM_LEN
+     macro.  So we have to define it here.  */
+#define TASK_COMM_LEN 16
+  if (len < TASK_COMM_LEN)
+    return ERANGE;
+
+  if (pd == THREAD_SELF)
+    return __prctl (PR_GET_NAME, buf) ? errno : 0;
+
+  /* Block all signals, as required by pd->exit_lock.  */
+  internal_sigset_t old_mask;
+  internal_signal_block_all (&old_mask);
+  __libc_lock_lock (pd->exit_lock);
+
+  int res = pd->tid > 0 ? getname (pd->tid, buf, len) : EINVAL;
+
+  __libc_lock_unlock (pd->exit_lock);
+  internal_signal_restore_set (&old_mask);
+
+  return res;
+}
 versioned_symbol (libc, __pthread_getname_np, pthread_getname_np,
 		  GLIBC_2_34);
 
diff --git a/sysdeps/pthread/tst-pthread-exited.c b/sysdeps/pthread/tst-pthread-exited.c
index 91c6533235..8f33de44b6 100644
--- a/sysdeps/pthread/tst-pthread-exited.c
+++ b/sysdeps/pthread/tst-pthread-exited.c
@@ -63,6 +63,12 @@ do_test (void)
     TEST_COMPARE (r, EINVAL);
   }
 
+  {
+    char thread_name[16];
+    int r = pthread_getname_np (thr, thread_name, sizeof (thread_name));
+    TEST_COMPARE (r, EINVAL);
+  }
+
   xpthread_join (thr);
 
   return 0;
-- 
2.47.2