[PATCH] D63908: hwasan: Improve precision of checks using short granule tags.
Peter Collingbourne via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Jun 27 17:17:33 PDT 2019
pcc created this revision.
pcc added a reviewer: eugenis.
Herald added subscribers: Sanitizers, cfe-commits, jfb, hiraditya, javed.absar, kubamracek.
Herald added projects: clang, Sanitizers, LLVM.
A short granule is a granule of size between 1 and `TG-1` bytes. The size
of a short granule is stored at the location in shadow memory where the
granule's tag is normally stored, while the granule's actual tag is stored
in the last byte of the granule. This means that in order to verify that a
pointer tag matches a memory tag, HWASAN must check for two possibilities:
- the pointer tag is equal to the memory tag in shadow memory, or
- the shadow memory tag is actually a short granule size, the value being loaded is in bounds of the granule and the pointer tag is equal to the last byte of the granule.
Pointer tags between 1 to `TG-1` are possible and are as likely as any other
tag. This means that these tags in memory have two interpretations: the full
tag interpretation (where the pointer tag is between 1 and `TG-1` and the
last byte of the granule is ordinary data) and the short tag interpretation
(where the pointer tag is stored in the granule).
When HWASAN detects an error near a memory tag between 1 and `TG-1`, it
will show both the memory tag and the last byte of the granule. Currently,
it is up to the user to disambiguate the two possibilities.
Because this functionality obsoletes the right aligned heap feature of
the HWASAN memory allocator (and because we can no longer easily test
it), the feature is removed.
Also update the documentation to cover both short granule tags and
outlined checks.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D63908
Files:
clang/docs/HardwareAssistedAddressSanitizerDesign.rst
compiler-rt/lib/hwasan/hwasan_allocator.cpp
compiler-rt/lib/hwasan/hwasan_checks.h
compiler-rt/lib/hwasan/hwasan_flags.inc
compiler-rt/lib/hwasan/hwasan_report.cpp
compiler-rt/lib/hwasan/hwasan_report.h
compiler-rt/test/hwasan/TestCases/heap-buffer-overflow.c
compiler-rt/test/hwasan/TestCases/random-align-right.c
compiler-rt/test/hwasan/TestCases/stack-oob.c
compiler-rt/test/hwasan/TestCases/tail-magic.c
llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
llvm/test/CodeGen/AArch64/hwasan-check-memaccess.ll
llvm/test/Instrumentation/HWAddressSanitizer/alloca-with-calls.ll
llvm/test/Instrumentation/HWAddressSanitizer/alloca.ll
llvm/test/Instrumentation/HWAddressSanitizer/basic.ll
llvm/test/Instrumentation/HWAddressSanitizer/kernel-alloca.ll
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