From 7bb7140df2b6fd5c1fee6c47488724bc256e957a Mon Sep 17 00:00:00 2001
From: Andrei Borzenkov <arvidjaar@gmail.com>
Date: Thu, 18 Jun 2015 20:09:47 +0300
Subject: [PATCH] fat: fix handling of "." and ".." directory entries

Emulate dot and dotdot in root directory. For other directories do not
add separator between name and extension for these two special entries.

Closes: 45335
---
 grub-core/fs/fat.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/grub-core/fs/fat.c b/grub-core/fs/fat.c
index 71537ff44..827708c18 100644
--- a/grub-core/fs/fat.c
+++ b/grub-core/fs/fat.c
@@ -829,7 +829,9 @@ grub_fat_iterate_dir_next (grub_disk_t disk, struct grub_fat_data *data,
 	      i--;
 	    }
 
-	  *filep++ = '.';
+	  /* XXX should we check that dir position is 0 or 1? */
+	  if (i > 2 || filep[0] != '.' || (i == 2 && filep[1] != '.'))
+	    *filep++ = '.';
 
 	  for (i = 8; i < 11 && ctxt->dir.name[i]; i++)
 	    *filep++ = grub_tolower (ctxt->dir.name[i]);
@@ -871,9 +873,31 @@ grub_fat_find_dir (grub_disk_t disk, struct grub_fat_data *data,
       return 0;
     }
 
-  /* Extract a directory name.  */
-  while (*path == '/')
-    path++;
+  do
+    {
+      /* Extract a directory name.  */
+      while (*path == '/')
+	path++;
+
+      /* Emulate special "." and ".." entries in root directory */
+      if (data->file_cluster == data->root_cluster)
+	{
+	  if (*path != '.')
+	    break;
+	  if (!path[1] || path[1] == '/')
+	    {
+	      path++;
+	      continue;
+	    }
+	  if (path[1] == '.' && (!path[2] || path[2] == '/'))
+	    {
+	      path += 2;
+	      continue;
+	    }
+	}
+      break;
+    }
+  while (1);
 
   dirp = grub_strchr (path, '/');
   if (dirp)
@@ -935,6 +959,9 @@ grub_fat_find_dir (grub_disk_t disk, struct grub_fat_data *data,
 	  data->file_size = grub_le_to_cpu32 (ctxt.dir.file_size);
 	  data->file_cluster = ((grub_le_to_cpu16 (ctxt.dir.first_cluster_high) << 16)
 				| grub_le_to_cpu16 (ctxt.dir.first_cluster_low));
+	  /* If directory points to root, starting cluster is 0 */
+	  if (!data->file_cluster)
+	    data->file_cluster = data->root_cluster;
 #endif
 	  data->cur_cluster_num = ~0U;