[tbb-commits] [tor-browser] 28/43: Bug 1743767 - Tighten bounds and add asserts for row-by-row ReadPixels. r=lsalzman, a=RyanVM

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pierov pushed a commit to branch tor-browser-91.10.0esr-11.0-1
in repository tor-browser.

commit cab7596edf3046a48a84dc8194b3a19217a40180
Author: Kelsey Gilbert <kelsey.gilbert at mozilla.com>
AuthorDate: Fri May 13 16:25:26 2022 -0400

    Bug 1743767 - Tighten bounds and add asserts for row-by-row ReadPixels. r=lsalzman, a=RyanVM
---
 dom/canvas/WebGLContextGL.cpp | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/dom/canvas/WebGLContextGL.cpp b/dom/canvas/WebGLContextGL.cpp
index 86957d730d955..b21bf2f57a98f 100644
--- a/dom/canvas/WebGLContextGL.cpp
+++ b/dom/canvas/WebGLContextGL.cpp
@@ -1203,13 +1203,20 @@ webgl::ReadPixelsResult WebGLContext::ReadPixelsImpl(
     desc2.srcOffset = {readX, readY};
     desc2.size = {rwSize.x, 1};
 
-    auto row = dest + writeX * bytesPerPixel;
-    row += writeY * rowStride;
-    for (const auto j : IntegerRange(size.y)) {
+    const auto skipBytes = writeX * bytesPerPixel;
+    const auto usedRowBytes = rwSize.x * bytesPerPixel;
+    for (const auto j : IntegerRange(rwSize.y)) {
       desc2.srcOffset.y = readY + j;
-      DoReadPixelsAndConvert(srcFormat->format, desc2, row, bytesNeeded,
-                             rowStride);
-      row += rowStride;
+      const auto destWriteBegin = dest + skipBytes + (writeY + j) * rowStride;
+      MOZ_RELEASE_ASSERT(dest <= destWriteBegin);
+      MOZ_RELEASE_ASSERT(destWriteBegin <= dest + availBytes);
+
+      const auto destWriteEnd = destWriteBegin + usedRowBytes;
+      MOZ_RELEASE_ASSERT(dest <= destWriteEnd);
+      MOZ_RELEASE_ASSERT(destWriteEnd <= dest + availBytes);
+
+      DoReadPixelsAndConvert(srcFormat->format, desc2, destWriteBegin,
+                             destWriteEnd - destWriteBegin, rowStride);
     }
   }
 

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