1From 8338a8238f08d9f3ae4c2ddfff0603eff80af9e2 Mon Sep 17 00:00:00 2001
2From: Daniel Axtens <dja@axtens.net>
3Date: Fri, 15 Jan 2021 14:06:46 +1100
4Subject: [PATCH] video/readers/jpeg: Don't decode data before start of stream
5
6When a start of stream marker is encountered, we call grub_jpeg_decode_sos()
7which allocates space for a bitmap.
8
9When a restart marker is encountered, we call grub_jpeg_decode_data() which
10then fills in that bitmap.
11
12If we get a restart marker before the start of stream marker, we will
13attempt to write to a bitmap_ptr that hasn't been allocated. Catch this
14and bail out. This fixes an attempt to write to NULL.
15
16Signed-off-by: Daniel Axtens <dja@axtens.net>
17Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
18Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
19---
20 grub-core/video/readers/jpeg.c | 4 ++++
21 1 file changed, 4 insertions(+)
22
23diff --git a/grub-core/video/readers/jpeg.c b/grub-core/video/readers/jpeg.c
24index e514812..e31602f 100644
25--- a/grub-core/video/readers/jpeg.c
26+++ b/grub-core/video/readers/jpeg.c
27@@ -646,6 +646,10 @@ grub_jpeg_decode_data (struct grub_jpeg_data *data)
28   nr1 = (data->image_height + vb - 1) >> (3 + data->log_vs);
29   nc1 = (data->image_width + hb - 1)  >> (3 + data->log_hs);
30
31+  if (data->bitmap_ptr == NULL)
32+    return grub_error(GRUB_ERR_BAD_FILE_TYPE,
33+		      "jpeg: attempted to decode data before start of stream");
34+
35   for (; data->r1 < nr1 && (!data->dri || rst);
36        data->r1++, data->bitmap_ptr += (vb * data->image_width - hb * nc1) * 3)
37     for (c1 = 0;  c1 < nc1 && (!data->dri || rst);
38--
392.14.2
40
41