[libglnx] shutil: Fix assertion failure in glnx_shutil_mkdir_p_at()

[Philip Withnall <pwithnall src gnome org>]

commit e30154431d7eea6397e5502b175ba3b50330140f
Author: Philip Withnall <withnall endlessm com>
Date:   Tue Sep 26 12:55:39 2017 +0100

    shutil: Fix assertion failure in glnx_shutil_mkdir_p_at()
    
    If the directory for @dfd is deleted after being opened,
    glnx_shutil_mkdir_p_at() would fail with an assertion failure. Fix that,
    and make it return an ENOENT error instead.
    
    Add a unit test.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>
    Reviewed-by: Colin Walters <walters verbum org>
    Reviewed-by: Jonathan Lebon <jlebon redhat com>
    
    https://github.com/ostreedev/ostree/issues/1215

 Makefile-libglnx.am         |    6 +++-
 glnx-shutil.c               |   11 +++++++-
 tests/test-libglnx-shutil.c |   63 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 2 deletions(-)
---
diff --git a/Makefile-libglnx.am b/Makefile-libglnx.am
index de6e49b..158063c 100644
--- a/Makefile-libglnx.am
+++ b/Makefile-libglnx.am
@@ -53,7 +53,7 @@ libglnx_la_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags)
 libglnx_la_LDFLAGS = -avoid-version -Bsymbolic-functions -export-symbols-regex "^glnx_" -no-undefined 
-export-dynamic 
 libglnx_la_LIBADD = $(libglnx_libs)
 
-libglnx_tests = test-libglnx-xattrs test-libglnx-fdio test-libglnx-errors test-libglnx-macros
+libglnx_tests = test-libglnx-xattrs test-libglnx-fdio test-libglnx-errors test-libglnx-macros 
test-libglnx-shutil
 TESTS += $(libglnx_tests)
 
 check_PROGRAMS += $(libglnx_tests)
@@ -72,3 +72,7 @@ test_libglnx_errors_LDADD = $(libglnx_libs) libglnx.la
 test_libglnx_macros_SOURCES = $(libglnx_srcpath)/tests/test-libglnx-macros.c
 test_libglnx_macros_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags)
 test_libglnx_macros_LDADD = $(libglnx_libs) libglnx.la
+
+test_libglnx_shutil_SOURCES = $(libglnx_srcpath)/tests/test-libglnx-shutil.c
+test_libglnx_shutil_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags)
+test_libglnx_shutil_LDADD = $(libglnx_libs) libglnx.la
diff --git a/glnx-shutil.c b/glnx-shutil.c
index 9124d7a..8438b5d 100644
--- a/glnx-shutil.c
+++ b/glnx-shutil.c
@@ -148,7 +148,13 @@ mkdir_p_at_internal (int              dfd,
           g_assert (!did_recurse);
 
           lastslash = strrchr (path, '/');
-          g_assert (lastslash != NULL);
+          if (lastslash == NULL)
+            {
+              /* This can happen if @dfd was deleted between being opened and
+               * passed to mkdir_p_at_internal(). */
+              return glnx_throw_errno_prefix (error, "mkdir(%s)", path);
+            }
+
           /* Note we can mutate the buffer as we dup'd it */
           *lastslash = '\0';
 
@@ -187,6 +193,9 @@ mkdir_p_at_internal (int              dfd,
  * directory fd @dfd.
  *
  * See also glnx_ensure_dir() for a non-recursive version.
+ *
+ * This will return %G_IO_ERROR_NOT_FOUND if @dfd has been deleted since being
+ * opened. It may return other errors from mkdirat() in other situations.
  */
 gboolean
 glnx_shutil_mkdir_p_at (int                   dfd,
diff --git a/tests/test-libglnx-shutil.c b/tests/test-libglnx-shutil.c
new file mode 100644
index 0000000..39f261b
--- /dev/null
+++ b/tests/test-libglnx-shutil.c
@@ -0,0 +1,63 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright © 2017 Endless Mobile, Inc.
+ *
+ * This 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 of the License, or (at your option) any later version.
+ *
+ * This 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 this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+#include "libglnx.h"
+#include <glib.h>
+#include <stdlib.h>
+#include <gio/gio.h>
+#include <err.h>
+#include <string.h>
+
+#include "libglnx-testlib.h"
+
+static void
+test_mkdir_p_enoent (void)
+{
+  _GLNX_TEST_DECLARE_ERROR(local_error, error);
+  glnx_fd_close int dfd = -1;
+
+  if (!glnx_ensure_dir (AT_FDCWD, "test", 0755, error))
+    return;
+  if (!glnx_opendirat (AT_FDCWD, "test", FALSE, &dfd, error))
+    return;
+  if (rmdir ("test") < 0)
+    return (void) glnx_throw_errno_prefix (error, "rmdir(%s)", "test");
+
+  /* This should fail with ENOENT. */
+  glnx_shutil_mkdir_p_at (dfd, "blah/baz", 0755, NULL, error);
+  g_assert_error (local_error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND);
+  g_clear_error (&local_error);
+}
+
+int
+main (int    argc,
+      char **argv)
+{
+  int ret;
+
+  g_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/mkdir-p/enoent", test_mkdir_p_enoent);
+
+  ret = g_test_run();
+
+  return ret;
+}