[PATCH 2/2] video/readers/jpeg: Check next_marker is within file size

[Alec Brown]

In grub-core/video/readers/jpeg.c, the function grub_jpeg_decode_huff_table()
has the variable next_marker which reads data from grub_jpeg_get_word() and
then uses it as an upper limit in a while loop. However, the function isn't
checking that next_marker is within the file size, so this check is being added
to the function.

Signed-off-by: Alec Brown <alec.r.brown@oracle.com>
---
 grub-core/video/readers/jpeg.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/grub-core/video/readers/jpeg.c b/grub-core/video/readers/jpeg.c
index 0eeea0e63..c0f95fbf9 100644
--- a/grub-core/video/readers/jpeg.c
+++ b/grub-core/video/readers/jpeg.c
@@ -199,6 +199,12 @@ grub_jpeg_decode_huff_table (struct grub_jpeg_data *data)
   next_marker = data->file->offset;
   next_marker += grub_jpeg_get_word (data);
 
+  if (next_marker > data->file->size)
+    {
+      /* Should never be set beyond the size of the file. */
+      return grub_error (GRUB_ERR_BAD_FILE_TYPE, "jpeg: invalid next 
reference");
+    }
+
   while (data->file->offset + sizeof (count) + 1 <= next_marker)
     {
       id = grub_jpeg_get_byte (data);
-- 
2.27.0