fb: Avoid potential out-of-bounds shift amounts in fbBlt

In fbBlt(), explicitly check (srcX < dstX) in the alternate shift calculation branch so that shift values (leftShift and rightShift) remain strictly within valid bit-width bounds [0..FB_UNIT - 1], avoiding potential 32-bit shift undefined behavior warnings
2026-10-21 01:13:38 +00:00 · 2026-08-30 01:10:31 +03:00 · 2026-08-30 01:10:31 +03:00 · b1571febfd
commit b1571febfd
parent c096eed016
1 changed files with 5 additions and 1 deletions
--- a/fb/fbblt.c
+++ b/fb/fbblt.c
@ -222,10 +222,14 @@ fbBlt(FbBits * srcLine,
            leftShift = srcX - dstX;
            rightShift = FB_UNIT - leftShift;
        }
-        else {
+        else if (srcX < dstX) {
            rightShift = dstX - srcX;
            leftShift = FB_UNIT - rightShift;
        }
+        else {
+            leftShift = 0;
+            rightShift = 0;
+        }
        while (height--) {
            src = srcLine;
            srcLine += srcStride;