Once we start instrumenting globals, all addresses including those of string literals
that we pass to the operating system will start being tagged. Since we can't rely
on the operating system to be able to cope with these addresses, we need to untag
them before passing them to the operating system. This change introduces a macro
that does so and uses it everywhere it is needed.
Differential Revision: https://reviews.llvm.org/D65768
llvm-svn: 367938
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.
Differential Revision: https://reviews.llvm.org/D63908
llvm-svn: 365551
Summary:
With free_checks_tail_magic=1 (default) HWASAN
writes magic bytes to the tail of every heap allocation
(last bytes of the last granule, if the last granule is not fully used)
and checks these bytes on free().
This feature will detect buffer overwires within the last granule
at the time of free().
This is an alternative to malloc_align_right=[1289] that should have
fewer compatibility issues. It is also weaker since it doesn't
detect read overflows and reports bugs at free() instead of at access.
Reviewers: eugenis
Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D54656
llvm-svn: 347116
Evgenii Stepanov