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

diff --git a/grub-core/fs/fat.c b/grub-core/fs/fat.c
index 71537ff4458b7717dbab564049b396b52e51b809..827708c18149a612ba79cdfadb1b7a8bfa79fd9f 100644 (file)
--- 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;