From d17a51bc59462b136635515e40019c8ae4e05b5e Mon Sep 17 00:00:00 2001
From: Ameer J <52414509+ameerj@users.noreply.github.com>
Date: Sun, 30 Jul 2023 13:05:45 -0400
Subject: extractbits robustness

---
 src/video_core/host_shaders/astc_decoder.comp | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

(limited to 'src/video_core/host_shaders')

diff --git a/src/video_core/host_shaders/astc_decoder.comp b/src/video_core/host_shaders/astc_decoder.comp
index 4277b0756..f65e1d1b9 100644
--- a/src/video_core/host_shaders/astc_decoder.comp
+++ b/src/video_core/host_shaders/astc_decoder.comp
@@ -349,14 +349,17 @@ uint ExtractBits(uvec4 payload, int offset, int bits) {
     if (bits <= 0) {
         return 0;
     }
-    int last_offset = offset + bits - 1;
-    int shifted_offset = offset >> 5;
+    if (bits > 32) {
+        return 0;
+    }
+    const int last_offset = offset + bits - 1;
+    const int shifted_offset = offset >> 5;
     if ((last_offset >> 5) == shifted_offset) {
         return bitfieldExtract(payload[shifted_offset], offset & 31, bits);
     }
-    int first_bits = 32 - (offset & 31);
-    int result_first = int(bitfieldExtract(payload[shifted_offset], offset & 31, first_bits));
-    int result_second = int(bitfieldExtract(payload[shifted_offset + 1], 0, bits - first_bits));
+    const int first_bits = 32 - (offset & 31);
+    const int result_first = int(bitfieldExtract(payload[shifted_offset], offset & 31, first_bits));
+    const int result_second = int(bitfieldExtract(payload[shifted_offset + 1], 0, bits - first_bits));
     return result_first | (result_second << first_bits);
 }
 
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