From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon, 23 Aug 2021 17:46:27 +0000 (-0300)
Subject: nptl: Use exit_lock when accessing TID on pthread_setname_np
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2518bb05f6a930d59ab574a443671323b900e79b;p=thirdparty%2Fglibc.git

nptl: Use exit_lock when accessing TID on pthread_setname_np

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

Checked on x86_64-linux-gnu.
---

diff --git a/nptl/pthread_setname.c b/nptl/pthread_setname.c
index 356d2e0368..a129335b3e 100644
--- a/nptl/pthread_setname.c
+++ b/nptl/pthread_setname.c
@@ -16,21 +16,40 @@
    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>
+static int
+setname (pid_t tid, const char *name, size_t name_len)
+{
+  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 EINVAL;
+
+  int res = 0;
+  ssize_t n = TEMP_FAILURE_RETRY (__write_nocancel (fd, name, name_len));
+  if (n < 0)
+    res = errno;
+  else if (n != name_len)
+    res = EIO;
+
+  __close_nocancel_nostatus (fd);
+
+  return res;
+}
 
 int
 __pthread_setname_np (pthread_t th, const char *name)
 {
-  const struct pthread *pd = (const struct pthread *) th;
+  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.  */
@@ -42,22 +61,15 @@ __pthread_setname_np (pthread_t th, const char *name)
   if (pd == THREAD_SELF)
     return __prctl (PR_SET_NAME, name) ? errno : 0;
 
-#define FMT "/proc/self/task/%u/comm"
-  char fname[sizeof (FMT) + 8];
-  sprintf (fname, FMT, (unsigned int) pd->tid);
+  /* 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 fd = __open64_nocancel (fname, O_RDWR);
-  if (fd == -1)
-    return errno;
-
-  int res = 0;
-  ssize_t n = TEMP_FAILURE_RETRY (__write_nocancel (fd, name, name_len));
-  if (n < 0)
-    res = errno;
-  else if (n != name_len)
-    res = EIO;
+  int res = pd->tid > 0 ? setname (pd->tid, name, name_len) : EINVAL;
 
-  __close_nocancel_nostatus (fd);
+  __libc_lock_unlock (pd->exit_lock);
+  internal_signal_restore_set (&old_mask);
 
   return res;
 }
diff --git a/sysdeps/pthread/tst-pthread-exited.c b/sysdeps/pthread/tst-pthread-exited.c
index 8f33de44b6..6a602afe3f 100644
--- a/sysdeps/pthread/tst-pthread-exited.c
+++ b/sysdeps/pthread/tst-pthread-exited.c
@@ -69,6 +69,12 @@ do_test (void)
     TEST_COMPARE (r, EINVAL);
   }
 
+  {
+    char thread_name[] = "test";
+    int r = pthread_setname_np (thr, thread_name);
+    TEST_COMPARE (r, EINVAL);
+  }
+
   xpthread_join (thr);
 
   return 0;