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[asan] Re-exec without ASLR if needed on 64-bit Linux #132682

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Merged
merged 2 commits into from
Mar 24, 2025
Merged

[asan] Re-exec without ASLR if needed on 64-bit Linux #132682

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[asan] Re-exec without ASLR if needed on 32-bit Linux
thurstond Mar 24, 2025
51980b3
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thurstond Mar 24, 2025
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14 changes: 8 additions & 6 deletions compiler-rt/lib/asan/asan_shadow_setup.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -109,12 +109,14 @@ void InitializeShadowMemory() {
ProtectGap(kShadowGap2Beg, kShadowGap2End - kShadowGap2Beg + 1);
ProtectGap(kShadowGap3Beg, kShadowGap3End - kShadowGap3Beg + 1);
} else {
// The shadow mappings can shadow the entire user address space. However,
// on 32-bit systems, the maximum ASLR entropy (currently up to 16-bits
// == 256MB) is a significant chunk of the address space; reclaiming it by
// disabling ASLR might allow chonky binaries to run.
if (sizeof(uptr) == 32)
TryReExecWithoutASLR();
// ASan's mappings can usually shadow the entire address space, even with
// maximum ASLR entropy. However:
// - On 32-bit systems, the maximum ASLR entropy (currently up to 16-bits
// == 256MB) is a significant chunk of the address space; reclaiming it
// by disabling ASLR might allow chonky binaries to run.
// - On 64-bit systems, some settings (e.g., for Linux, unlimited stack
// size plus 31+ bits of entropy) can lead to an incompatible layout.
TryReExecWithoutASLR();

Report(
"Shadow memory range interleaves with an existing memory mapping. "
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