[libcxx-commits] [libcxx] 60ac394 - [ASan][libc++] Annotating `std::basic_string` with all allocators (#75845)
via libcxx-commits
libcxx-commits at lists.llvm.org
Sat Jan 13 09:11:58 PST 2024
Author: Tacet
Date: 2024-01-13T18:11:53+01:00
New Revision: 60ac394dc9ed617f802b33c3b9ac8881ca6a940c
URL: https://github.com/llvm/llvm-project/commit/60ac394dc9ed617f802b33c3b9ac8881ca6a940c
DIFF: https://github.com/llvm/llvm-project/commit/60ac394dc9ed617f802b33c3b9ac8881ca6a940c.diff
LOG: [ASan][libc++] Annotating `std::basic_string` with all allocators (#75845)
This commit turns on ASan annotations in `std::basic_string` for all
allocators by default.
Originally suggested here: https://reviews.llvm.org/D146214
String annotations added here:
https://github.com/llvm/llvm-project/pull/72677
This commit is part of our efforts to support container annotations with
(almost) every allocator. Annotating `std::basic_string` with default
allocator is implemented in
https://github.com/llvm/llvm-project/pull/72677.
Additionally it removes `__begin != nullptr` because `data()` should
never return a nullptr.
Support in ASan API exists since
https://github.com/llvm/llvm-project/commit/1c5ad6d2c01294a0decde43a88e9c27d7437d157.
This patch removes the check in std::basic_string annotation member
function (__annotate_contiguous_container) to support different
allocators.
You can turn off annotations for a specific allocator based on changes
from
https://github.com/llvm/llvm-project/commit/2fa1bec7a20bb23f2e6620085adb257dafaa3be0.
The motivation for a 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 call to `std::equal` 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.
If you have any questions, please email:
- advenam.tacet at trailofbits.com
- disconnect3d at trailofbits.com
Added:
libcxx/test/libcxx/containers/strings/basic.string/asan.pass.cpp
libcxx/test/libcxx/containers/strings/basic.string/asan_turning_off.pass.cpp
Modified:
libcxx/include/string
libcxx/test/support/asan_testing.h
Removed:
################################################################################
diff --git a/libcxx/include/string b/libcxx/include/string
index bdc9a6e5616fd1..e97139206d4fa7 100644
--- a/libcxx/include/string
+++ b/libcxx/include/string
@@ -1891,8 +1891,7 @@ private:
#if !defined(_LIBCPP_HAS_NO_ASAN) && defined(_LIBCPP_INSTRUMENTED_WITH_ASAN)
const void* __begin = data();
const void* __end = data() + capacity() + 1;
- if (!__libcpp_is_constant_evaluated() && __begin != nullptr &&
- is_same<allocator_type, __default_allocator_type>::value)
+ if (__asan_annotate_container_with_allocator<allocator_type>::value && !__libcpp_is_constant_evaluated())
__sanitizer_annotate_contiguous_container(__begin, __end, __old_mid, __new_mid);
#endif
}
diff --git a/libcxx/test/libcxx/containers/strings/basic.string/asan.pass.cpp b/libcxx/test/libcxx/containers/strings/basic.string/asan.pass.cpp
new file mode 100644
index 00000000000000..c7e0924be3df6f
--- /dev/null
+++ b/libcxx/test/libcxx/containers/strings/basic.string/asan.pass.cpp
@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: asan
+// UNSUPPORTED: c++03
+
+// Basic test if ASan annotations work for basic_string.
+
+#include <string>
+#include <cassert>
+#include <cstdlib>
+
+#include "asan_testing.h"
+#include "min_allocator.h"
+#include "test_iterators.h"
+#include "test_macros.h"
+
+extern "C" void __sanitizer_set_death_callback(void (*callback)(void));
+
+void do_exit() { exit(0); }
+
+int main(int, char**) {
+ {
+ typedef cpp17_input_iterator<char*> MyInputIter;
+ // Should not trigger ASan.
+ std::basic_string<char, std::char_traits<char>, safe_allocator<char>> v;
+ char i[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'a', 'b', 'c', 'd', 'e',
+ 'f', 'g', 'h', 'i', 'j', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};
+
+ v.insert(v.begin(), MyInputIter(i), MyInputIter(i + 29));
+ assert(v[0] == 'a');
+ assert(is_string_asan_correct(v));
+ }
+
+ __sanitizer_set_death_callback(do_exit);
+ {
+ using T = char;
+ using C = std::basic_string<T, std::char_traits<T>, safe_allocator<T>>;
+ const T t[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'a', 'b', 'c', 'd', 'e',
+ 'f', 'g', 'h', 'i', 'j', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'};
+ C c(std::begin(t), std::end(t));
+ assert(is_string_asan_correct(c));
+ assert(__sanitizer_verify_contiguous_container(c.data(), c.data() + c.size() + 1, c.data() + c.capacity() + 1) !=
+ 0);
+ T foo = c[c.size() + 1]; // should trigger ASAN and call do_exit().
+ assert(false); // if we got here, ASAN didn't trigger
+ ((void)foo);
+
+ return 0;
+ }
+}
diff --git a/libcxx/test/libcxx/containers/strings/basic.string/asan_turning_off.pass.cpp b/libcxx/test/libcxx/containers/strings/basic.string/asan_turning_off.pass.cpp
new file mode 100644
index 00000000000000..c8ee17c580a4c4
--- /dev/null
+++ b/libcxx/test/libcxx/containers/strings/basic.string/asan_turning_off.pass.cpp
@@ -0,0 +1,102 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: asan
+// UNSUPPORTED: c++03
+
+// Test based on: https://bugs.chromium.org/p/chromium/issues/detail?id=1419798#c5
+// Some allocators during deallocation may not call destructors and just reuse memory.
+// In those situations, one may want to deactivate annotations for a specific allocator.
+// It's possible with __asan_annotate_container_with_allocator template class.
+// This test confirms that those allocators work after turning off annotations.
+//
+// A context to this test is a situations when memory is repurposed and destructors are not called.
+// Related issue: https://github.com/llvm/llvm-project/issues/60384
+//
+// That issue appeared in the past and was addressed here: https://reviews.llvm.org/D145628
+//
+// There was also a discussion, if it's UB.
+// Related discussion: https://reviews.llvm.org/D136765#4155262
+// Related notes: https://eel.is/c++draft/basic.life#6
+// Probably it's no longer UB due a change in CWG2523.
+// https://cplusplus.github.io/CWG/issues/2523.html
+//
+// Therefore we make sure that it works that way, also because people rely on this behavior.
+// Annotations are turned off only, if a user explicitly turns off annotations for a specific allocator.
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string>
+#include <new>
+
+// Allocator with pre-allocated (with malloc in constructor) buffers.
+// Memory may be freed without calling destructors.
+struct reuse_allocator {
+ static size_t const N = 100;
+ reuse_allocator() {
+ for (size_t i = 0; i < N; ++i)
+ __buffers[i] = malloc(8 * 1024);
+ }
+ ~reuse_allocator() {
+ for (size_t i = 0; i < N; ++i)
+ free(__buffers[i]);
+ }
+ void* alloc() {
+ assert(__next_id < N);
+ return __buffers[__next_id++];
+ }
+ void reset() { __next_id = 0; }
+ void* __buffers[N];
+ size_t __next_id = 0;
+} reuse_buffers;
+
+template <typename T>
+struct user_allocator {
+ using value_type = T;
+ user_allocator() = default;
+ template <class U>
+ user_allocator(user_allocator<U>) {}
+ friend bool operator==(user_allocator, user_allocator) { return true; }
+ friend bool operator!=(user_allocator x, user_allocator y) { return !(x == y); }
+
+ T* allocate(size_t n) {
+ if (n * sizeof(T) > 8 * 1024)
+ throw std::bad_array_new_length();
+ return (T*)reuse_buffers.alloc();
+ }
+ void deallocate(T*, size_t) noexcept {}
+};
+
+// Turn off annotations for user_allocator:
+template <class T>
+struct std::__asan_annotate_container_with_allocator<user_allocator<T>> {
+ static bool const value = false;
+};
+
+int main(int, char**) {
+ using S = std::basic_string<char, std::char_traits<char>, user_allocator<char>>;
+
+ {
+ // Create a string with a buffer from reuse allocator object:
+ S* s = new (reuse_buffers.alloc()) S();
+ // Use string, so it's poisoned, if container annotations for that allocator are not turned off:
+ for (int i = 0; i < 40; i++)
+ s->push_back('a');
+ }
+ // Reset the state of the allocator, don't call destructors, allow memory to be reused:
+ reuse_buffers.reset();
+ {
+ // Create a next string with the same allocator, so the same buffer due to the reset:
+ S s;
+ // Use memory inside the string again, if it's poisoned, an error will be raised:
+ for (int i = 0; i < 60; i++)
+ s.push_back('a');
+ }
+
+ return 0;
+}
diff --git a/libcxx/test/support/asan_testing.h b/libcxx/test/support/asan_testing.h
index 2dfec5c42b00b2..6bfc8280a4ead3 100644
--- a/libcxx/test/support/asan_testing.h
+++ b/libcxx/test/support/asan_testing.h
@@ -75,7 +75,7 @@ TEST_CONSTEXPR bool is_string_asan_correct(const std::basic_string<ChrT, TraitsT
return true;
if (!is_string_short(c) || _LIBCPP_SHORT_STRING_ANNOTATIONS_ALLOWED) {
- if (std::is_same<Alloc, std::allocator<ChrT>>::value)
+ if (std::__asan_annotate_container_with_allocator<Alloc>::value)
return __sanitizer_verify_contiguous_container(c.data(), c.data() + c.size() + 1, c.data() + c.capacity() + 1) !=
0;
else
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