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Summary:
Initially, Scudo had a monolithic design where both C and C++ functions were
living in the same library. This was not necessarily ideal, and with the work
on -fsanitize=scudo, it became more apparent that this needed to change.
We are splitting the new/delete interceptor in their own C++ library. This
allows more flexibility, notably with regard to std::bad_alloc when the work is
done. This also allows us to not link new & delete when using pure C.
Additionally, we add the UBSan runtimes with Scudo, in order to be able to have
a -fsanitize=scudo,undefined in Clang (see work in D39334).
The changes in this patch:
- split the cxx specific code in the scudo cmake file into a new library;
(remove the spurious foreach loop, that was not necessary)
- add the UBSan runtimes (both C and C++);
- change the test cmake file to allow for specific C & C++ tests;
- make C tests pure C, rename their extension accordingly.
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: srhines, mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D39461
llvm-svn: 317097
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Summary:
Mark Android as supported in the cmake configuration for Scudo.
Scudo is not added yet in the Android build bots, but code builds and tests
pass locally. It is for a later CL. I also checked that Scudo builds as part
of the Android toolchain.
A few modifications had to be made:
- Android defaults to `abort_on_error=1`, which doesn't work well with the
current tests. So change the default way to pass `SCUDO_OPTIONS` to the tests
to account for this, setting it to 0 by default;
- Disable the `valloc.cpp` & `random_shuffle.cpp` tests on Android;
- There is a bit of gymnatic to be done with the `SCUDO_TEST_TARGET_ARCH`
string, due to android using the `-android` suffix, and `i686` instead of
`i386`;
- Android doesn't need `-lrt`.
Reviewers: alekseyshl, eugenis
Reviewed By: alekseyshl
Subscribers: srhines, mgorny, llvm-commits
Differential Revision: https://reviews.llvm.org/D37907
llvm-svn: 313538
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Summary:
First, some context.
The main feedback we get about the quarantine is that it's too memory hungry.
A single MB of quarantine will have an impact of 3 to 4MB of PSS/RSS, and
things quickly get out of hand in terms of memory usage, and the quarantine
ends up disabled.
The main objective of the quarantine is to protect from use-after-free
exploitation by making it harder for an attacker to reallocate a controlled
chunk in place of the targeted freed chunk. This is achieved by not making it
available to the backend right away for reuse, but holding it a little while.
Historically, what has usually been the target of such attacks was objects,
where vtable pointers or other function pointers could constitute a valuable
targeti to replace. Those are usually on the smaller side. There is barely any
advantage in putting the quarantine several megabytes of RGB data or the like.
Now for the patch.
This patch introduces a new way the Quarantine behaves in Scudo. First of all,
the size of the Quarantine will be defined in KB instead of MB, then we
introduce a new option: the size up to which (lower than or equal to) a chunk
will be quarantined. This way, we only quarantine smaller chunks, and the size
of the quarantine remains manageable. It also prevents someone from triggering
a recycle by allocating something huge. We default to 512 bytes on 32-bit and
2048 bytes on 64-bit platforms.
In details, the patches includes the following:
- introduce `QuarantineSizeKb`, but honor `QuarantineSizeMb` if set to fall
back to the old behavior (meaning no threshold in that case);
`QuarantineSizeMb` is described as deprecated in the options descriptios;
documentation update will follow;
- introduce `QuarantineChunksUpToSize`, the new threshold value;
- update the `quarantine.cpp` test, and other tests using `QuarantineSizeMb`;
- remove `AllocatorOptions::copyTo`, it wasn't used;
- slightly change the logic around `quarantineOrDeallocateChunk` to accomodate
for the new logic; rename a couple of variables there as well;
Rewriting the tests, I found a somewhat annoying bug where non-default aligned
chunks would account for more than needed when placed in the quarantine due to
`<< MinAlignment` instead of `<< MinAlignmentLog`. This is fixed and tested for
now.
Reviewers: alekseyshl, kcc
Reviewed By: alekseyshl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D35694
llvm-svn: 308884
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Summary:
The local and global quarantine sizes were not offering a distinction for
32-bit and 64-bit platforms. This is addressed with lower values for 32-bit.
When writing additional tests for the quarantine, it was discovered that when
calling some of the allocator interface function prior to any allocation
operation having occured, the test would crash due to the allocator not being
initialized. This was addressed by making sure the allocator is initialized
for those scenarios.
Relevant tests were added in interface.cpp and quarantine.cpp.
Last change being the removal of the extraneous link dependencies for the
tests thanks to rL293220, anf the addition of the gc-sections linker flag.
Reviewers: kcc, alekseyshl
Reviewed By: alekseyshl
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D29341
llvm-svn: 294037
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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
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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
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