From 5bbd7d0bf21393a42a7c5939b4cdfcbb5175c844 Mon Sep 17 00:00:00 2001
From: Maxim Suhanov <[email protected]>
Date: Mon, 28 Aug 2023 16:33:44 +0300
Subject: [PATCH 3/5] fs/ntfs: Fix an OOB read when parsing bitmaps for index
 attributes

This fix introduces checks to ensure that bitmaps for directory indices
are never read beyond their actual sizes.

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

Reported-by: Maxim Suhanov <[email protected]>
Signed-off-by: Maxim Suhanov <[email protected]>
Reviewed-by: Daniel Kiper <[email protected]>
---
 grub-core/fs/ntfs.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/grub-core/fs/ntfs.c b/grub-core/fs/ntfs.c
index c0150441a..24045669e 100644
--- a/grub-core/fs/ntfs.c
+++ b/grub-core/fs/ntfs.c
@@ -839,6 +839,25 @@ grub_ntfs_iterate_dir (grub_fshelp_node_t dir,
 
 	  if (is_resident)
 	    {
+              if (bitmap_len > (at->mft->data->mft_size << GRUB_NTFS_BLK_SHR))
+		{
+		  grub_error (GRUB_ERR_BAD_FS, "resident bitmap too large");
+		  goto done;
+		}
+
+              if (cur_pos >= at->mft->buf + (at->mft->data->mft_size << GRUB_NTFS_BLK_SHR))
+		{
+		  grub_error (GRUB_ERR_BAD_FS, "resident bitmap out of range");
+		  goto done;
+		}
+
+              if (u16at (cur_pos, 0x14) + u32at (cur_pos, 0x10) >
+		  (grub_addr_t) at->mft->buf + (at->mft->data->mft_size << GRUB_NTFS_BLK_SHR) - (grub_addr_t) cur_pos)
+		{
+		  grub_error (GRUB_ERR_BAD_FS, "resident bitmap out of range");
+		  goto done;
+		}
+
               grub_memcpy (bmp, cur_pos + u16at (cur_pos, 0x14),
                            bitmap_len);
 	    }
-- 
2.41.0