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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Daniel Axtens <dja@axtens.net>
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Date: Tue, 6 Jul 2021 19:19:11 +1000
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Subject: [PATCH] video/readers/png: Sanity check some huffman codes
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ASAN picked up two OOB global reads: we weren't checking if some code
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values fit within the cplens or cpdext arrays. Check and throw an error
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if not.
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Signed-off-by: Daniel Axtens <dja@axtens.net>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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(cherry picked from commit c3a8ab0cbd24153ec7b1f84a96ddfdd72ef8d117)
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---
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 grub-core/video/readers/png.c | 6 ++++++
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 1 file changed, 6 insertions(+)
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diff --git a/grub-core/video/readers/png.c b/grub-core/video/readers/png.c
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index d7ed5aa6cf..7f2ba7849b 100644
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--- a/grub-core/video/readers/png.c
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+++ b/grub-core/video/readers/png.c
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@@ -753,6 +753,9 @@ grub_png_read_dynamic_block (struct grub_png_data *data)
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 	  int len, dist, pos;
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 	  n -= 257;
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+	  if (((unsigned int) n) >= ARRAY_SIZE (cplens))
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+	    return grub_error (GRUB_ERR_BAD_FILE_TYPE,
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+			       "png: invalid huff code");
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 	  len = cplens[n];
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 	  if (cplext[n])
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 	    len += grub_png_get_bits (data, cplext[n]);
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@@ -760,6 +763,9 @@ grub_png_read_dynamic_block (struct grub_png_data *data)
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 	    return grub_errno;
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 	  n = grub_png_get_huff_code (data, &data->dist_table);
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+	  if (((unsigned int) n) >= ARRAY_SIZE (cpdist))
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+	    return grub_error (GRUB_ERR_BAD_FILE_TYPE,
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+			       "png: invalid huff code");
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 	  dist = cpdist[n];
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 	  if (cpdext[n])
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 	    dist += grub_png_get_bits (data, cpdext[n]);