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[compiler-rt][msan] Fix 32-bit overflow in CheckMemoryLayoutSanity (#189199)

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Use start + (end - start) / 2 instead of (start + end) / 2 to compute
the midpoint address. The original expression overflows when start + end
exceeds UPTR_MAX, which happens on 32-bit targets whose memory layout
includes regions above 0x80000000.
This commit is contained in:
Brian Cain
2026-03-28 22:14:52 -05:00
committed by GitHub
parent 89d57d03bf
commit 670de1f522
1 changed files with 3 additions and 2 deletions
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5
compiler-rt/lib/msan/msan_linux.cpp
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@@ -90,7 +90,8 @@ static void CheckMemoryLayoutSanity() {
CHECK_LT(start, end);
CHECK_EQ(prev_end, start);
CHECK(addr_is_type(start, type));
CHECK(addr_is_type((start + end) / 2, type));
// Use start + (end - start) / 2 to avoid overflow on 32-bit.
CHECK(addr_is_type(start + (end - start) / 2, type));
CHECK(addr_is_type(end - 1, type));
if (type == MappingDesc::APP || type == MappingDesc::ALLOCATOR) {
uptr addr = start;
@@ -98,7 +99,7 @@ static void CheckMemoryLayoutSanity() {
CHECK(MEM_IS_ORIGIN(MEM_TO_ORIGIN(addr)));
CHECK_EQ(MEM_TO_ORIGIN(addr), SHADOW_TO_ORIGIN(MEM_TO_SHADOW(addr)));
addr = (start + end) / 2;
addr = start + (end - start) / 2;
CHECK(MEM_IS_SHADOW(MEM_TO_SHADOW(addr)));
CHECK(MEM_IS_ORIGIN(MEM_TO_ORIGIN(addr)));
CHECK_EQ(MEM_TO_ORIGIN(addr), SHADOW_TO_ORIGIN(MEM_TO_SHADOW(addr)));