This revision is a part of a series of patches extending AddressSanitizer C++ container overflow detection capabilities by adding annotations, similar to those existing in `std::vector`, to `std::string` and `std::deque` collections. These changes allow ASan to detect cases when the instrumented program accesses memory which is internally allocated by the collection but is still not in-use (accesses before or after the stored elements for `std::deque`, or between the size and capacity bounds for `std::string`).
The motivation for the research and those changes was a bug, found by Trail of Bits, in a real code where an out-of-bounds read could happen as two strings were compared via a std::equals function that took `iter1_begin`, `iter1_end`, `iter2_begin` iterators (with a custom comparison function). When object `iter1` was longer than `iter2`, read out-of-bounds on `iter2` could happen. Container sanitization would detect it.
This revision introduces annotations for `std::deque`. Each chunk of the container can now be annotated using the `__sanitizer_annotate_double_ended_contiguous_container` function, which was added in the rG1c5ad6d2c01294a0decde43a88e9c27d7437d157. Any attempt to access poisoned memory will trigger an ASan error. Although false negatives are rare, they are possible due to limitations in the ASan API, where a few (usually up to 7) bytes before the container may remain unpoisoned. There are no false positives in the same way as with `std::vector` annotations.
This patch only supports objects (deques) that use the standard allocator. However, it can be easily extended to support all allocators, as suggested in the D146815 revision.
Furthermore, the patch includes the addition of the `is_double_ended_contiguous_container_asan_correct` function to `libcxx/test/support/asan_testing.h`. This function can be used to verify whether a `std::deque` object has been correctly annotated.
Finally, the patch extends the unit tests to verify ASan annotations (added LIBCPP_ASSERTs).
If a program is compiled without ASan, all helper functions will be no-ops. In binaries with ASan, there is a negligible performance impact since the code from the change is only executed when the deque container changes in size and it’s proportional to the change. It is important to note that regardless of whether or not these changes are in use, every access to the container's memory is instrumented.
If you have any questions, please email:
- advenam.tacet@trailofbits.com
- disconnect3d@trailofbits.com
Reviewed By: #libc, philnik
Differential Revision: https://reviews.llvm.org/D132092
This revision is a part of a series of patches extending AddressSanitizer C++ container overflow detection capabilities by adding annotations, similar to those existing in std::vector, to std::string and `std::deque` collections. These changes allow ASan to detect cases when the instrumented program accesses memory which is internally allocated by the collection but is still not in-use (accesses before or after the stored elements for `std::deque`, or between the size and capacity bounds for `std::string`).
The motivation for the research and those changes was a bug, found by Trail of Bits, in a real code where an out-of-bounds read could happen as two strings were compared via a std::equals function that took `iter1_begin`, `iter1_end`, `iter2_begin` iterators (with a custom comparison function). When object `iter1` was longer than `iter2`, read out-of-bounds on `iter2` could happen. Container sanitization would detect it.
This revision introduces annotations for `std::deque`. Each chunk of the container can now be annotated using the `__sanitizer_annotate_double_ended_contiguous_container` function, which was added in the rG1c5ad6d2c01294a0decde43a88e9c27d7437d157. Any attempt to access poisoned memory will trigger an ASan error. Although false negatives are rare, they are possible due to limitations in the ASan API, where a few (usually up to 7) bytes before the container may remain unpoisoned. There are no false positives in the same way as with `std::vector` annotations.
This patch only supports objects (deques) that use the standard allocator. However, it can be easily extended to support all allocators, as suggested in the D146815 revision.
Furthermore, the patch includes the addition of the `is_double_ended_contiguous_container_asan_correct` function to libcxx/test/support/asan_testing.h. This function can be used to verify whether a `std::deque` object has been correctly annotated.
Finally, the patch extends the unit tests to verify ASan annotations (added LIBCPP_ASSERTs).
If a program is compiled without ASan, all helper functions will be no-ops. In binaries with ASan, there is a negligible performance impact since the code from the change is only executed when the deque container changes in size and it’s proportional to the change. It is important to note that regardless of whether or not these changes are in use, every access to the container's memory is instrumented.
Reviewed By: #libc, philnik
Spies: vitalybuka, hans, mikhail.ramalho, Enna1, #sanitizers, philnik, libcxx-commits
Differential Revision: https://reviews.llvm.org/D132092
This revision is a part of a series of patches extending AddressSanitizer C++ container overflow detection capabilities by adding annotations, similar to those existing in std::vector, to std::string and `std::deque` collections. These changes allow ASan to detect cases when the instrumented program accesses memory which is internally allocated by the collection but is still not in-use (accesses before or after the stored elements for `std::deque`, or between the size and capacity bounds for `std::string`).
The motivation for the research and those changes was a bug, found by Trail of Bits, in a real code where an out-of-bounds read could happen as two strings were compared via a std::equals function that took `iter1_begin`, `iter1_end`, `iter2_begin` iterators (with a custom comparison function). When object `iter1` was longer than `iter2`, read out-of-bounds on `iter2` could happen. Container sanitization would detect it.
This revision introduces annotations for `std::deque`. Each chunk of the container can now be annotated using the `__sanitizer_annotate_double_ended_contiguous_container` function, which was added in the rG1c5ad6d2c01294a0decde43a88e9c27d7437d157. Any attempt to access poisoned memory will trigger an ASan error. Although false negatives are rare, they are possible due to limitations in the ASan API, where a few (usually up to 7) bytes before the container may remain unpoisoned. There are no false positives in the same way as with `std::vector` annotations.
This patch only supports objects (deques) that use the standard allocator. However, it can be easily extended to support all allocators, as suggested in the D146815 revision.
Furthermore, the patch includes the addition of the `is_double_ended_contiguous_container_asan_correct` function to libcxx/test/support/asan_testing.h. This function can be used to verify whether a `std::deque` object has been correctly annotated.
Finally, the patch extends the unit tests to verify ASan annotations (added LIBCPP_ASSERTs).
If a program is compiled without ASan, all helper functions will be no-ops. In binaries with ASan, there is a negligible performance impact since the code from the change is only executed when the deque container changes in size and it’s proportional to the change. It is important to note that regardless of whether or not these changes are in use, every access to the container's memory is instrumented.
Reviewed By: #libc, philnik
Spies: mikhail.ramalho, Enna1, #sanitizers, philnik, libcxx-commits
Differential Revision: https://reviews.llvm.org/D132092
Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I'd like to make libc++ behave better with what freestanding should
be, so that it can be a tool we use in improving the standard. To do that we
need to try stuff out, both with "freestanding the language mode" and
"freestanding the library subset".
Let's start with the super basic: run the libc++ tests in freestanding, using
clang as the compiler, and see what works. The easiest hack to do this:
In utils/libcxx/test/config.py add:
self.cxx.compile_flags += ['-ffreestanding']
Run the tests and they all fail.
Why? Because in freestanding `main` isn't special. This "not special" property
has two effects: main doesn't get mangled, and main isn't allowed to omit its
`return` statement. The first means main gets mangled and the linker can't
create a valid executable for us to test. The second means we spew out warnings
(ew) and the compiler doesn't insert the `return` we omitted, and main just
falls of the end and does whatever undefined behavior (if you're luck, ud2
leading to non-zero return code).
Let's start my work with the basics. This patch changes all libc++ tests to
declare `main` as `int main(int, char**` so it mangles consistently (enabling us
to declare another `extern "C"` main for freestanding which calls the mangled
one), and adds `return 0;` to all places where it was missing. This touches 6124
files, and I apologize.
The former was done with The Magic Of Sed.
The later was done with a (not quite correct but decent) clang tool:
https://gist.github.com/jfbastien/793819ff360baa845483dde81170feed
This works for most tests, though I did have to adjust a few places when e.g.
the test runs with `-x c`, macros are used for main (such as for the filesystem
tests), etc.
Once this is in we can create a freestanding bot which will prevent further
regressions. After that, we can start the real work of supporting C++
freestanding fairly well in libc++.
<rdar://problem/47754795>
Reviewers: ldionne, mclow.lists, EricWF
Subscribers: christof, jkorous, dexonsmith, arphaman, miyuki, libcxx-commits
Differential Revision: https://reviews.llvm.org/D57624
llvm-svn: 353086
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351648
