[PATCH] D68676: [ASan] Do not misrepresent high value address dereferences as null dereferences

[Julian Lettner via Phabricator via llvm-commits]

yln created this revision.
Herald added a reviewer: jfb.
Herald added projects: Sanitizers, LLVM.
Herald added subscribers: llvm-commits, Sanitizers.

Dereferences with addresses above the 48-bit hardware addressable range
produce "invalid instruction" (instead of "invalid access") hardware
exceptions (there is no hardware address decoding logic for those bits),
and the address provided by this exception is the address of the
instruction (not the faulting address).  The kernel maps the "invalid
instruction" to SEGV, but fails to provide the real fault address.

Because of this ASan lies and says that those cases are null
dereferences.  This downgrades the severity of a found bug in terms of
security.  In the ASan signal handler, we can not provide the real
faulting address, but at least we can try not to lie.

rdar://50366151


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D68676

Files:
  compiler-rt/lib/asan/asan_errors.h
  compiler-rt/lib/sanitizer_common/sanitizer_common.h
  compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp
  compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_report.cpp
  compiler-rt/lib/sanitizer_common/sanitizer_win.cpp
  compiler-rt/test/asan/TestCases/Darwin/high-address-dereference.c

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