From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Tue, 6 Jul 2021 19:19:11 +1000
Subject: [PATCH] video/readers/png: Sanity check some huffman codes

ASAN picked up two OOB global reads: we weren't checking if some code
values fit within the cplens or cpdext arrays. Check and throw an error
if not.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
(cherry picked from commit c3a8ab0cbd24153ec7b1f84a96ddfdd72ef8d117)
---
 grub-core/video/readers/png.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/grub-core/video/readers/png.c b/grub-core/video/readers/png.c
index d7ed5aa6cf..7f2ba7849b 100644
--- a/grub-core/video/readers/png.c
+++ b/grub-core/video/readers/png.c
@@ -753,6 +753,9 @@ grub_png_read_dynamic_block (struct grub_png_data *data)
 	  int len, dist, pos;
 
 	  n -= 257;
+	  if (((unsigned int) n) >= ARRAY_SIZE (cplens))
+	    return grub_error (GRUB_ERR_BAD_FILE_TYPE,
+			       "png: invalid huff code");
 	  len = cplens[n];
 	  if (cplext[n])
 	    len += grub_png_get_bits (data, cplext[n]);
@@ -760,6 +763,9 @@ grub_png_read_dynamic_block (struct grub_png_data *data)
 	    return grub_errno;
 
 	  n = grub_png_get_huff_code (data, &data->dist_table);
+	  if (((unsigned int) n) >= ARRAY_SIZE (cpdist))
+	    return grub_error (GRUB_ERR_BAD_FILE_TYPE,
+			       "png: invalid huff code");
 	  dist = cpdist[n];
 	  if (cpdext[n])
 	    dist += grub_png_get_bits (data, cpdext[n]);