Summary:
In an effort to getting rid of dependencies to external libraries, we are
replacing atomic PackedHeader use of std::atomic with Sanitizer's
atomic_uint64_t, which allows us to avoid -latomic.
Reviewers: kcc, phosek, alekseyshl
Reviewed By: alekseyshl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D28864
llvm-svn: 292630
Summary:
ARM & AArch64 runtime detection for hardware support of CRC32 has been added
via check of the AT_HWVAL auxiliary vector.
Following Michal's suggestions in D28417, the CRC32 code has been further
changed and looks better now. When compiled with full relro (which is strongly
suggested to benefit from additional hardening), the weak symbol for
computeHardwareCRC32 is read-only and the assembly generated is fairly clean
and straight forward. As suggested, an additional optimization is to skip
the runtime check if SSE 4.2 has been enabled globally, as opposed to only
for scudo_crc32.cpp.
scudo_crc32.h has no purpose anymore and was removed.
Reviewers: alekseyshl, kcc, rengolin, mgorny, phosek
Reviewed By: rengolin, mgorny
Subscribers: aemerson, rengolin, llvm-commits
Differential Revision: https://reviews.llvm.org/D28574
llvm-svn: 292409
Summary:
As raised in D28304, enabling SSE 4.2 for the whole Scudo tree leads to the
emission of SSE 4.2 instructions everywhere, while the runtime checks only
applied to the CRC32 computing function.
This patch separates the CRC32 function taking advantage of the hardware into
its own file, and only enabled -msse4.2 for that file, if detected to be
supported by the compiler.
Another consequence of removing SSE4.2 globally is realizing that memcpy were
not being optimized, which turned out to be due to the -fno-builtin in
SANITIZER_COMMON_CFLAGS. So we now explicitely enable builtins for Scudo.
The resulting assembly looks good, with some CALLs are introduced instead of
the CRC32 code being inlined.
Reviewers: kcc, mgorny, alekseyshl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D28417
llvm-svn: 291570
Summary:
With the recent changes to the Secondary, we use less bits for UnusedBytes,
which allows us in return to increase the bits used for Offset. That means
that we can use a Primary SizeClassMap allowing for a larger maximum size.
Reviewers: kcc, alekseyshl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D27816
llvm-svn: 289838
Summary:
I atually had an integer overflow on 32-bit with D27428 that didn't reproduce
locally, as the test servers would manage allocate addresses in the 0xffffxxxx
range, which led to some issues when rounding addresses.
At this point, I feel that Scudo could benefit from having its own combined
allocator, as we don't get any benefit from the current one, but have to work
around some hurdles (alignment checks, rounding up that is no longer needed,
extraneous code).
Reviewers: kcc, alekseyshl
Subscribers: llvm-commits, kubabrecka
Differential Revision: https://reviews.llvm.org/D27681
llvm-svn: 289572
Summary:
This update introduces i386 support for the Scudo Hardened Allocator, and
offers software alternatives for functions that used to require hardware
specific instruction sets. This should make porting to new architectures
easier.
Among the changes:
- The chunk header has been changed to accomodate the size limitations
encountered on 32-bit architectures. We now fit everything in 64-bit. This
was achieved by storing the amount of unused bytes in an allocation rather
than the size itself, as one can be deduced from the other with the help
of the GetActuallyAllocatedSize function. As it turns out, this header can
be used for both 64 and 32 bit, and as such we dropped the requirement for
the 128-bit compare and exchange instruction support (cmpxchg16b).
- Add 32-bit support for the checksum and the PRNG functions: if the SSE 4.2
instruction set is supported, use the 32-bit CRC32 instruction, and in the
XorShift128, use a 32-bit based state instead of 64-bit.
- Add software support for CRC32: if SSE 4.2 is not supported, fallback on a
software implementation.
- Modify tests that were not 32-bit compliant, and expand them to cover more
allocation and alignment sizes. The random shuffle test has been deactivated
for linux-i386 & linux-i686 as the 32-bit sanitizer allocator doesn't
currently randomize chunks.
Reviewers: alekseyshl, kcc
Subscribers: filcab, llvm-commits, tberghammer, danalbert, srhines, mgorny, modocache
Differential Revision: https://reviews.llvm.org/D26358
llvm-svn: 288255
Summary:
In order to avoid starting a separate thread to return unused memory to
the system (the thread interferes with process startup on Android,
Zygota waits for all threads to exit before fork, but this thread never
exits), try to return it right after free.
Reviewers: eugenis
Subscribers: cryptoad, filcab, danalbert, kubabrecka, llvm-commits
Patch by Aleksey Shlyapnikov.
Differential Revision: https://reviews.llvm.org/D27003
llvm-svn: 288091
Summary:
In order to support 32-bit platforms, we have to make some adjustments in
multiple locations, one of them being the Scudo chunk header. For it to fit on
64 bits (as a reminder, on x64 it's 128 bits), I had to crunch the space taken
by some of the fields. In order to keep the offset field small, the secondary
allocator was changed to accomodate aligned allocations for larger alignments,
hence making the offset constant for chunks serviced by it.
The resulting header candidate has been added, and further modifications to
allow 32-bit support will follow.
Another notable change is the addition of MaybeStartBackgroudThread() to allow
release of the memory to the OS.
Reviewers: kcc
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D25688
llvm-svn: 285209
Summary:
s/CHECK_LT/CHECK_LE/ in the secondary allocator, as under certain circumstances
Ptr + Size can be equal to MapEnd. This edge case was not found by the current
tests, so those were extended to be able to catch that.
Reviewers: kcc
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D25101
llvm-svn: 282913
Summary:
The Sanitizer Secondary Allocator was not entirely ideal was Scudo for several
reasons: decent amount of unneeded code, redundant checks already performed by
the front end, unneeded data structures, difficulty to properly protect the
secondary chunks header.
Given that the second allocator is pretty straight forward, Scudo will use its
own, trimming all the unneeded code off of the Sanitizer one. A significant
difference in terms of security is that now each secondary chunk is preceded
and followed by a guard page, thus mitigating overflows into and from the
chunk.
A test was added as well to illustrate the overflow & underflow situations
into the guard pages.
Reviewers: kcc
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D24737
llvm-svn: 281938
Summary:
Currently, the Scudo Hardened Allocator only gets its flags via the SCUDO_OPTIONS environment variable.
With this patch, we offer the opportunity for programs to define their own options via __scudo_default_options() which behaves like __asan_default_options() (weak symbol).
A relevant test has been added as well, and the documentation updated accordingly.
I also used this patch as an opportunity to rename a few variables to comply with the LLVM naming scheme, and replaced a use of Report with dieWithMessage for consistency (and to avoid a callback).
Reviewers: llvm-commits, kcc
Differential Revision: https://reviews.llvm.org/D23018
llvm-svn: 277536
Summary:
This is an initial implementation of a Hardened Allocator based on Sanitizer Common's CombinedAllocator.
It aims at mitigating heap based vulnerabilities by adding several features to the base allocator, while staying relatively fast.
The following were implemented:
- additional consistency checks on the allocation function parameters and on the heap chunks;
- use of checksum protected chunk header, to detect corruption;
- randomness to the allocator base;
- delayed freelist (quarantine), to mitigate use after free and overall determinism.
Additional mitigations are in the works.
Reviewers: eugenis, aizatsky, pcc, krasin, vitalybuka, glider, dvyukov, kcc
Subscribers: kubabrecka, filcab, llvm-commits
Differential Revision: http://reviews.llvm.org/D20084
llvm-svn: 271968
Kostya Kortchinsky