From 690bee69fae6b4bd911293d6b7e56774e29fdf64 Mon Sep 17 00:00:00 2001
From: Daniel Axtens <dja@axtens.net>
Date: Tue, 6 Jul 2021 19:19:11 +1000
Subject: 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.

Reference:https://git.savannah.gnu.org/cgit/grub.git/commit/?id=690bee69fae6b4bd911293d6b7e56774e29fdf64
Conflict:NA

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 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 d7ed5aa..7f2ba78 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]);
-- 
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