From 2af9e56c2306dc9d80a4476fa5b154a26a935557 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 16 Jul 2020 03:37:10 -0700
Subject: [PATCH] nptl: Zero-extend arguments to SETXID syscalls [BZ #26248]

nptl has

/* Opcodes and data types for communication with the signal handler to
   change user/group IDs.  */
struct xid_command
{
  int syscall_no;
  long int id[3];
  volatile int cntr;
  volatile int error;
};

 /* This must be last, otherwise the current thread might not have
     permissions to send SIGSETXID syscall to the other threads.  */
  result = INTERNAL_SYSCALL_NCS (cmdp->syscall_no, 3,
                                 cmdp->id[0], cmdp->id[1], cmdp->id[2]);

But the second argument of setgroups syscal is a pointer:

       int setgroups(size_t size, const gid_t *list);

But on x32, pointers passed to syscall must have pointer type so that they
will be zero-extended.  Since the XID arguments are unsigned on the kernel
side, so no sign extension is required.  Change xid_command to

struct xid_command
{
  int syscall_no;
  unsigned long int id[3];
  volatile int cntr;
  volatile int error;
};

so that all arguments zero-extended.  A testcase is added for x32 and
setgroups returned with EFAULT when running as root without the fix.
---
 nptl/descr.h                                  |  8 ++-
 sysdeps/unix/sysv/linux/x86_64/x32/Makefile   |  4 ++
 .../sysv/linux/x86_64/x32/tst-setgroups.c     | 67 +++++++++++++++++++
 3 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 sysdeps/unix/sysv/linux/x86_64/x32/tst-setgroups.c

diff --git a/nptl/descr.h b/nptl/descr.h
index 6a509b6725..e98fe4084d 100644
--- a/nptl/descr.h
+++ b/nptl/descr.h
@@ -95,7 +95,13 @@ struct pthread_unwind_buf
 struct xid_command
 {
   int syscall_no;
-  long int id[3];
+  /* Enforce zero-extension for the pointer argument in
+
+     int setgroups(size_t size, const gid_t *list);
+
+     Since the XID arguments are unsigned on the kernel side, so no sign
+     extension is required.  */
+  unsigned long int id[3];
   volatile int cntr;
   volatile int error; /* -1: no call yet, 0: success seen, >0: error seen.  */
 };
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/Makefile b/sysdeps/unix/sysv/linux/x86_64/x32/Makefile
index 16b768d8ba..1a6c984f96 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/Makefile
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/Makefile
@@ -5,6 +5,10 @@ ifeq ($(subdir),misc)
 sysdep_routines += arch_prctl
 endif
 
+ifeq ($(subdir),nptl)
+xtests += tst-setgroups
+endif
+
 ifeq ($(subdir),conform)
 # For bugs 16437 and 21279.
 conformtest-xfail-conds += x86_64-x32-linux
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/tst-setgroups.c b/sysdeps/unix/sysv/linux/x86_64/x32/tst-setgroups.c
new file mode 100644
index 0000000000..9895443278
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/tst-setgroups.c
@@ -0,0 +1,67 @@
+/* Basic test for setgroups
+   Copyright (C) 2020 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 <stdlib.h>
+#include <limits.h>
+#include <grp.h>
+#include <errno.h>
+#include <error.h>
+#include <support/xthread.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+#include <support/xunistd.h>
+
+static void *
+start_routine (void *args)
+{
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  int size;
+  /* NB: Stack address is at 0xfffXXXXX.  */
+  gid_t list[NGROUPS_MAX];
+  int status = EXIT_SUCCESS;
+
+  pthread_t thread = xpthread_create (NULL, start_routine, NULL);
+
+  size = getgroups (sizeof (list) / sizeof (list[0]), list);
+  if (size < 0)
+    {
+      status = EXIT_FAILURE;
+      error (0, errno, "getgroups failed");
+    }
+  if (setgroups (size, list) < 0)
+    {
+      if (errno == EPERM)
+	status = EXIT_UNSUPPORTED;
+      else
+	{
+	  status = EXIT_FAILURE;
+	  error (0, errno, "setgroups failed");
+	}
+    }
+
+  xpthread_join (thread);
+
+  return status;
+}
+
+#include <support/test-driver.c>
-- 
2.26.2

