kern/file: Ensure file->data is set

This is to avoid a generic issue were some filesystems would not set
data and also not set a grub_errno. This meant it was possible for many
filesystems to grub_dl_unref() themselves multiple times resulting in
it being possible to unload the filesystems while there were still
references to them, e.g., via a loopback.

Reported-by: B Horn <b@horn.uk>
Signed-off-by: B Horn <b@horn.uk>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/kern/file.c b/grub-core/kern/file.c
index 750177248f9d3b2e7a07836686b49b38bb4417b7..e990507fca003c70b1c4df7797149270330a9dd4 100644 (file)
--- a/grub-core/kern/file.c
+++ b/grub-core/kern/file.c
@@ -114,6 +114,9 @@ grub_file_open (const char *name, enum grub_file_type type)
   if ((file->fs->fs_open) (file, file_name) != GRUB_ERR_NONE)
     goto fail;
 
+  if (file->data == NULL)
+    goto fail;
+
   file->name = grub_strdup (name);
   grub_errno = GRUB_ERR_NONE;