[SECURITY PATCH 3/6] fs/ntfs: Fix an OOB read when parsing directory entries from resident and non-resident index attributes

[Daniel Kiper]

From: Maxim Suhanov <dfirblog@gmail.com>

This fix introduces checks to ensure that index entries are never read
beyond the corresponding directory index.

The lack of this check is a minor issue, likely not exploitable in any way.

Reported-by: Maxim Suhanov <dfirblog@gmail.com>
Signed-off-by: Maxim Suhanov <dfirblog@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/ntfs.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/grub-core/fs/ntfs.c b/grub-core/fs/ntfs.c
index a68e173d8..2d78b96e1 100644
--- a/grub-core/fs/ntfs.c
+++ b/grub-core/fs/ntfs.c
@@ -599,7 +599,7 @@ get_utf8 (grub_uint8_t *in, grub_size_t len)
 }
 
 static int
-list_file (struct grub_ntfs_file *diro, grub_uint8_t *pos,
+list_file (struct grub_ntfs_file *diro, grub_uint8_t *pos, grub_uint8_t 
*end_pos,
           grub_fshelp_iterate_dir_hook_t hook, void *hook_data)
 {
   grub_uint8_t *np;
@@ -610,6 +610,9 @@ list_file (struct grub_ntfs_file *diro, grub_uint8_t *pos,
       grub_uint8_t namespace;
       char *ustr;
 
+      if ((pos >= end_pos) || (end_pos - pos < 0x52))
+        break;
+
       if (pos[0xC] & 2)                /* end signature */
        break;
 
@@ -617,6 +620,9 @@ list_file (struct grub_ntfs_file *diro, grub_uint8_t *pos,
       ns = *(np++);
       namespace = *(np++);
 
+      if (2 * ns > end_pos - pos - 0x52)
+        break;
+
       /*
        *  Ignore files in DOS namespace, as they will reappear as Win32
        *  names.
@@ -806,7 +812,9 @@ grub_ntfs_iterate_dir (grub_fshelp_node_t dir,
     }
 
   cur_pos += 0x10;             /* Skip index root */
-  ret = list_file (mft, cur_pos + u16at (cur_pos, 0), hook, hook_data);
+  ret = list_file (mft, cur_pos + u16at (cur_pos, 0),
+                   at->mft->buf + (at->mft->data->mft_size << 
GRUB_NTFS_BLK_SHR),
+                   hook, hook_data);
   if (ret)
     goto done;
 
@@ -893,6 +901,7 @@ grub_ntfs_iterate_dir (grub_fshelp_node_t dir,
                             (const grub_uint8_t *) "INDX")))
                goto done;
              ret = list_file (mft, &indx[0x18 + u16at (indx, 0x18)],
+                              indx + (mft->data->idx_size << 
GRUB_NTFS_BLK_SHR),
                               hook, hook_data);
              if (ret)
                goto done;
-- 
2.11.0