From d14d5705807c8216f3cfb1de3af6f448a1401599 Mon Sep 17 00:00:00 2001
From: Campbell Barton <campbell@blender.org>
Date: Fri, 15 Jul 2022 14:52:32 +1000
Subject: blend_render_info: add check for negative BHead length (corrupt file)

Without this check, corrupt files would raise a Python exception,
now early exit with a useful error.
---
 release/scripts/modules/blend_render_info.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/release/scripts/modules/blend_render_info.py b/release/scripts/modules/blend_render_info.py
index 37c5f6dd3ba..6b45a6f7e72 100755
--- a/release/scripts/modules/blend_render_info.py
+++ b/release/scripts/modules/blend_render_info.py
@@ -93,6 +93,11 @@ def _read_blend_rend_chunk_from_file(blendfile, filepath):
             break
 
         sizeof_data_left = struct.unpack('>i' if is_big_endian else '<i', blendfile.read(4))[0]
+        if sizeof_data_left < 0:
+            # Very unlikely, but prevent other errors.
+            sys.stderr.write("Negative block size found (corrupt file): %s\n" % filepath)
+            break
+
         # 4 from the `head_id`, another 4 for the size of the BHEAD.
         sizeof_bhead_left = sizeof_bhead - 8
 
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