Linux: readdir64_r should not skip d_ino == 0 entries (bug 32126)

This is the same bug as bug 12165, but for readdir_r.  The
regression test covers both bug 12165 and bug 32126.

Reviewed-by: DJ Delorie <dj@redhat.com>

dirent/Makefile

@@ -62,6 +62,7 @@ tests := \
   tst-fdopendir \
   tst-fdopendir2 \
   tst-readdir-long \
+  tst-readdir-zero-inode \
   tst-rewinddir \
   tst-scandir \
   tst-scandir64 \

dirent/tst-readdir-zero-inode.c

@@ -0,0 +1,134 @@
+/* Test that readdir does not skip entries with d_ino == 0 (bug 12165).
+   Copyright (C) 2024 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 <support/check.h>
+#include <support/fuse.h>
+#include <support/readdir.h>
+#include <support/xdirent.h>
+
+/* Add the directory entry at OFFSET to the stream D.  */
+static uint64_t
+add_directory_entry (struct support_fuse_dirstream *d, uint64_t offset)
+{
+  bool added = false;
+  ++offset;
+  switch (offset - 1)
+    {
+    case 0:
+      added = support_fuse_dirstream_add (d, 1, offset, DT_DIR, ".");
+      break;
+    case 1:
+      added = support_fuse_dirstream_add (d, 1, offset, DT_DIR, "..");
+      break;
+    case 2:
+      added = support_fuse_dirstream_add (d, 2, offset, DT_REG, "before");
+      break;
+    case 3:
+      added = support_fuse_dirstream_add (d, 0, offset, DT_REG, "zero");
+      break;
+    case 4:
+      added = support_fuse_dirstream_add (d, 3, offset, DT_REG, "after");
+      break;
+    }
+  if (added)
+    return offset;
+  else
+    return 0;
+}
+
+/* Set to true if getdents64 should produce only one entry.  */
+static bool one_entry_per_getdents64;
+
+static void
+fuse_thread (struct support_fuse *f, void *closure)
+{
+  struct fuse_in_header *inh;
+  while ((inh = support_fuse_next (f)) != NULL)
+    {
+      if (support_fuse_handle_mountpoint (f)
+          || (inh->nodeid == 1 && support_fuse_handle_directory (f)))
+        continue;
+      switch (inh->opcode)
+        {
+        case FUSE_READDIR:
+          if (inh->nodeid == 1)
+            {
+              uint64_t offset = support_fuse_cast (READ, inh)->offset;
+              struct support_fuse_dirstream *d
+                = support_fuse_prepare_readdir (f);
+              while (true)
+                {
+                  offset = add_directory_entry (d, offset);
+                  if (offset == 0 || one_entry_per_getdents64)
+                    break;
+                }
+              support_fuse_reply_prepared (f);
+            }
+          else
+            support_fuse_reply_error (f, EIO);
+          break;
+        default:
+          FAIL ("unexpected event %s", support_fuse_opcode (inh->opcode));
+          support_fuse_reply_error (f, EIO);
+        }
+    }
+}
+
+static int
+do_test (void)
+{
+  support_fuse_init ();
+
+  for (enum support_readdir_op op = 0; op <= support_readdir_op_last (); ++op)
+    {
+      struct support_fuse *f = support_fuse_mount (fuse_thread, NULL);
+      DIR *dir = xopendir (support_fuse_mountpoint (f));
+      struct support_dirent e = { 0, };
+
+      TEST_VERIFY (support_readdir (dir, op, &e));
+      TEST_COMPARE_STRING (e.d_name, ".");
+      TEST_COMPARE (e.d_ino, 1);
+
+      TEST_VERIFY (support_readdir (dir, op, &e));
+      TEST_COMPARE_STRING (e.d_name, "..");
+      TEST_COMPARE (e.d_ino, 1);
+
+      TEST_VERIFY (support_readdir (dir, op, &e));
+      TEST_COMPARE_STRING (e.d_name, "before");
+      TEST_COMPARE (e.d_ino, 2);
+
+      TEST_VERIFY (support_readdir (dir, op, &e));
+      TEST_COMPARE_STRING (e.d_name, "zero");
+      TEST_COMPARE (e.d_ino, 0);
+
+      TEST_VERIFY (support_readdir (dir, op, &e));
+      TEST_COMPARE_STRING (e.d_name, "after");
+      TEST_COMPARE (e.d_ino, 3);
+
+      TEST_VERIFY (!support_readdir (dir, op, &e));
+
+      free (e.d_name);
+      xclosedir (dir);
+      support_fuse_unmount (f);
+    }
+
+  return 0;
+}
+
+#include <support/test-driver.c>

sysdeps/unix/sysv/linux/readdir64_r.c

@@ -37,7 +37,7 @@ __readdir64_r (DIR *dirp, struct dirent64 *entry, struct dirent64 **result)
 
   __libc_lock_lock (dirp->lock);
 
-  do
+  while (1)
     {
       if (dirp->offset >= dirp->size)
 	{
@@ -79,26 +79,21 @@ __readdir64_r (DIR *dirp, struct dirent64 *entry, struct dirent64 **result)
 
       dirp->filepos = dp->d_off;
 
-      if (reclen > offsetof (struct dirent64, d_name) + NAME_MAX + 1)
+      if (reclen <= offsetof (struct dirent64, d_name) + NAME_MAX + 1)
-	{
+	break;
+
       /* The record is very long.  It could still fit into the
-	     caller-supplied buffer if we can skip padding at the
+	 caller-supplied buffer if we can skip padding at the end.  */
-	     end.  */
       size_t namelen = _D_EXACT_NAMLEN (dp);
       if (namelen <= NAME_MAX)
-	    reclen = offsetof (struct dirent64, d_name) + namelen + 1;
-	  else
 	{
-	      /* The name is too long.  Ignore this file.  */
+	  reclen = offsetof (struct dirent64, d_name) + namelen + 1;
-	      dirp->errcode = ENAMETOOLONG;
+	  break;
-	      dp->d_ino = 0;
-	      continue;
-	    }
 	}
 
-      /* Skip deleted and ignored files.  */
+      /* The name is too long.  Ignore this file.  */
+      dirp->errcode = ENAMETOOLONG;
     }
-  while (dp->d_ino == 0);
 
   if (dp != NULL)
     {