From 05aa64ac71242bff90a2356a319d6373b44d7d10 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Fri, 15 Jan 2021 12:57:04 +1100
Subject: [PATCH] video/readers/jpeg: Catch files with unsupported quantization
 or Huffman tables

Our decoder only supports 2 quantization tables. If a file asks for
a quantization table with index > 1, reject it.

Similarly, our decoder only supports 4 Huffman tables. If a file asks
for a Huffman table with index > 3, reject it.

This fixes some out of bounds reads. It's not clear what degree of control
over subsequent execution could be gained by someone who can carefully
set up the contents of memory before loading an invalid JPEG file.

Reference: http://git.savannah.gnu.org/cgit/grub.git/commit/?id=693989598fd38c3c0b2a928f4f64865b5681762f

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/video/readers/jpeg.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/grub-core/video/readers/jpeg.c b/grub-core/video/readers/jpeg.c
index 0b6ce3c..23f919a 100644
--- a/grub-core/video/readers/jpeg.c
+++ b/grub-core/video/readers/jpeg.c
@@ -333,7 +333,11 @@ grub_jpeg_decode_sof (struct grub_jpeg_data *data)
       else if (ss != JPEG_SAMPLING_1x1)
 	return grub_error (GRUB_ERR_BAD_FILE_TYPE,
 			   "jpeg: sampling method not supported");
+
       data->comp_index[id][0] = grub_jpeg_get_byte (data);
+      if (data->comp_index[id][0] > 1)
+	return grub_error (GRUB_ERR_BAD_FILE_TYPE,
+			   "jpeg: too many quantization tables");
     }
 
   if (data->file->offset != next_marker)
@@ -602,6 +606,10 @@ grub_jpeg_decode_sos (struct grub_jpeg_data *data)
       ht = grub_jpeg_get_byte (data);
       data->comp_index[id][1] = (ht >> 4);
       data->comp_index[id][2] = (ht & 0xF) + 2;
+
+      if ((data->comp_index[id][1] < 0) || (data->comp_index[id][1] > 3) ||
+	  (data->comp_index[id][2] < 0) || (data->comp_index[id][2] > 3))
+	return grub_error (GRUB_ERR_BAD_FILE_TYPE, "jpeg: invalid hufftable index");
     }
 
   grub_jpeg_get_byte (data);	/* Skip 3 unused bytes.  */
-- 
2.19.1