Fix addition/overflow checks.

For unsigned arithmetic, use:

(a + b < a) to detect whether a+b wraps
(a > c / b) to detect whether a*b > c

Bug: 120078455
Test: builds and boots
Change-Id: Ic4f4d44f7c0656caa115f90f4cfa130192914949
(cherry picked from commit da2f2fd0f4c4eeb498b4b0541719f4f34faf13e2)

1 files changed, 2 insertions, 1 deletions

diff --git a/libs/binder/BufferedTextOutput.cpp b/libs/binder/BufferedTextOutput.cpp
index 857bbf9510..2978b539d7 100644
--- a/libs/binder/BufferedTextOutput.cpp
+++ b/libs/binder/BufferedTextOutput.cpp
@@ -49,9 +49,10 @@ struct BufferedTextOutput::BufferState : public RefBase
     }
     
     status_t append(const char* txt, size_t len) {
+        if (len > SIZE_MAX - bufferPos) return NO_MEMORY; // overflow
         if ((len+bufferPos) > bufferSize) {
+            if ((len + bufferPos) > SIZE_MAX / 3) return NO_MEMORY; // overflow
             size_t newSize = ((len+bufferPos)*3)/2;
-            if (newSize < (len+bufferPos)) return NO_MEMORY;    // overflow
             void* b = realloc(buffer, newSize);
             if (!b) return NO_MEMORY;
             buffer = (char*)b;