* src/c++17/memory_resource.cc (bitset::full()): Handle edge case
for _M_next_word maximum value.
(bitset::get_first_unset(), bitset::set(size_type)): Use
update_next_word() to update _M_next_word.
(bitset::update_next_word()): New function, avoiding wraparound of
unsigned _M_next_word member.
(bitset::max_word_index()): New function.
(chunk::chunk(void*, uint32_t, void*, size_t)): Add assertion.
(chunk::max_bytes_per_chunk()): New function.
(pool::replenish(memory_resource*, const pool_options&)): Prevent
_M_blocks_per_chunk from exceeding max_blocks_per_chunk or from
causing chunk::max_bytes_per_chunk() to be exceeded.
* testsuite/20_util/unsynchronized_pool_resource/allocate-max-chunks.cc:
New test.
Tested x86_64-linux, committed to trunk.
commit 9e6c1cedf054342beb710163c5b01137dcf07d45
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Mon Nov 12 22:50:36 2018 +0000
Fix overflows in std::pmr::unsynchonized_pool_resource
* src/c++17/memory_resource.cc (bitset::full()): Handle edge case
for _M_next_word maximum value.
(bitset::get_first_unset(), bitset::set(size_type)): Use
update_next_word() to update _M_next_word.
(bitset::update_next_word()): New function, avoiding wraparound of
unsigned _M_next_word member.
(bitset::max_word_index()): New function.
(chunk::chunk(void*, uint32_t, void*, size_t)): Add assertion.
(chunk::max_bytes_per_chunk()): New function.
(pool::replenish(memory_resource*, const pool_options&)): Prevent
_M_blocks_per_chunk from exceeding max_blocks_per_chunk or from
causing chunk::max_bytes_per_chunk() to be exceeded.
*
testsuite/20_util/unsynchronized_pool_resource/allocate-max-chunks.cc:
New test.
diff --git a/libstdc++-v3/src/c++17/memory_resource.cc
b/libstdc++-v3/src/c++17/memory_resource.cc
index 3595e255889..fdbbc914f2e 100644
--- a/libstdc++-v3/src/c++17/memory_resource.cc
+++ b/libstdc++-v3/src/c++17/memory_resource.cc
@@ -290,7 +290,18 @@ namespace pmr
}
// True if all bits are set
- bool full() const noexcept { return _M_next_word >= nwords(); }
+ bool full() const noexcept
+ {
+ if (_M_next_word >= nwords())
+ return true;
+ // For a bitset with size() > (max_blocks_per_chunk() - 64) we will
+ // have nwords() == (max_word_index() + 1) and so _M_next_word will
+ // never be equal to nwords().
+ // In that case, check if the last word is full:
+ if (_M_next_word == max_word_index())
+ return _M_words[_M_next_word] == word(-1);
+ return false;
+ }
// True if size() != 0 and no bits are set.
bool empty() const noexcept
@@ -343,11 +354,7 @@ namespace pmr
const word bit = word(1) << n;
_M_words[i] |= bit;
if (i == _M_next_word)
- {
- while (_M_words[_M_next_word] == word(-1)
- && ++_M_next_word != nwords())
- { }
- }
+ update_next_word();
return (i * bits_per_word) + n;
}
}
@@ -361,11 +368,7 @@ namespace pmr
const word bit = word(1) << (n % bits_per_word);
_M_words[wd] |= bit;
if (wd == _M_next_word)
- {
- while (_M_words[_M_next_word] == word(-1)
- && ++_M_next_word != nwords())
- { }
- }
+ update_next_word();
}
void clear(size_type n) noexcept
@@ -378,6 +381,18 @@ namespace pmr
_M_next_word = wd;
}
+ // Update _M_next_word to refer to the next word with an unset bit.
+ // The size of the _M_next_word bit-field means it cannot represent
+ // the maximum possible nwords() value. To avoid wraparound to zero
+ // this function saturates _M_next_word at max_word_index().
+ void update_next_word() noexcept
+ {
+ size_t next = _M_next_word;
+ while (_M_words[next] == word(-1) && ++next < nwords())
+ { }
+ _M_next_word = std::min(next, max_word_index());
+ }
+
void swap(bitset& b) noexcept
{
std::swap(_M_words, b._M_words);
@@ -396,6 +411,10 @@ namespace pmr
static constexpr size_t max_blocks_per_chunk() noexcept
{ return (1ull << _S_size_digits) - 1; }
+ // Maximum value that can be stored in bitset::_M_next_word member (8191).
+ static constexpr size_t max_word_index() noexcept
+ { return (max_blocks_per_chunk() + bits_per_word - 1) / bits_per_word; }
+
word* data() const noexcept { return _M_words; }
private:
@@ -425,7 +444,7 @@ namespace pmr
: bitset(words, n),
_M_bytes(bytes),
_M_p(static_cast<std::byte*>(p))
- { }
+ { __glibcxx_assert(bytes <= chunk::max_bytes_per_chunk()); }
chunk(chunk&& c) noexcept
: bitset(std::move(c)), _M_bytes(c._M_bytes), _M_p(c._M_p)
@@ -451,6 +470,9 @@ namespace pmr
// Number of blocks in this chunk
using bitset::size;
+ static constexpr uint32_t max_bytes_per_chunk() noexcept
+ { return numeric_limits<decltype(_M_bytes)>::max(); }
+
// Determine if block with address p and size block_size
// is contained within this chunk.
bool owns(void* p, size_t block_size)
@@ -639,8 +661,7 @@ namespace pmr
void replenish(memory_resource* __r, const pool_options& __opts)
{
using word = chunk::word;
- const size_t __blocks
- = std::min<size_t>(__opts.max_blocks_per_chunk, _M_blocks_per_chunk);
+ const size_t __blocks = _M_blocks_per_chunk;
const auto __bits = chunk::bits_per_word;
const size_t __words = (__blocks + __bits - 1) / __bits;
const size_t __block_size = block_size();
@@ -658,7 +679,16 @@ namespace pmr
__r->deallocate(__p, __bytes, __alignment);
}
if (_M_blocks_per_chunk < __opts.max_blocks_per_chunk)
- _M_blocks_per_chunk *= 2;
+ {
+ const size_t max_blocks
+ = (chunk::max_bytes_per_chunk() - sizeof(word))
+ / (__block_size + 0.125);
+ _M_blocks_per_chunk = std::min({
+ max_blocks,
+ __opts.max_blocks_per_chunk,
+ (size_t)_M_blocks_per_chunk * 2
+ });
+ }
}
void release(memory_resource* __r)
diff --git
a/libstdc++-v3/testsuite/20_util/unsynchronized_pool_resource/allocate-max-chunks.cc
b/libstdc++-v3/testsuite/20_util/unsynchronized_pool_resource/allocate-max-chunks.cc
new file mode 100644
index 00000000000..f995fe9a47b
--- /dev/null
+++
b/libstdc++-v3/testsuite/20_util/unsynchronized_pool_resource/allocate-max-chunks.cc
@@ -0,0 +1,88 @@
+// Copyright (C) 2018 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++17" }
+// { dg-do run { target c++17 } }
+
+#include <memory_resource>
+#include <testsuite_hooks.h>
+
+struct custom_mr : std::pmr::memory_resource
+{
+ custom_mr(std::size_t max) : max(max) { }
+
+ bool reached_max = false;
+
+private:
+ std::size_t max;
+ std::size_t count = 0;
+
+ void* do_allocate(std::size_t b, std::size_t a)
+ {
+ if (b >= max)
+ reached_max = true;
+ count += b;
+ if (count > (18 * 1024 * 1024))
+ // Something went wrong, should not need to allocate this much.
+ throw std::bad_alloc();
+ return std::pmr::new_delete_resource()->allocate(b, a);
+ }
+
+ void do_deallocate(void* p, std::size_t b, std::size_t a)
+ { std::pmr::new_delete_resource()->deallocate(p, b, a); }
+
+ bool do_is_equal(const memory_resource& r) const noexcept
+ { return false; }
+};
+
+void
+test01()
+{
+ // Only going to allocate blocks of this size:
+ const std::size_t block_size = 8;
+ std::pmr::pool_options opts{};
+ // Use maximum allowed number of blocks per chunk:
+ opts.max_blocks_per_chunk = (std::size_t)-1;
+ opts.largest_required_pool_block = block_size;
+ {
+ std::pmr::unsynchronized_pool_resource r(opts);
+ // Get the real max_blocks_per_chunk that will be used:
+ opts = r.options();
+ // Sanity test in case chunk::max_blocks_per_chunk() changes,
+ // as that could make this test take much longer to run:
+ VERIFY( opts.max_blocks_per_chunk <= (1 << 19) );
+ }
+ custom_mr c(block_size * opts.max_blocks_per_chunk);
+ std::pmr::unsynchronized_pool_resource r(opts, &c);
+ // Keep allocating from the pool until reaching the maximum chunk size:
+ while (!c.reached_max)
+ (void) r.allocate(block_size, 1);
+ c.reached_max = false;
+ // Now fill that maximally-sized chunk
+ // (this used to go into an infinite loop ):
+ for (std::size_t i = 0; i < opts.max_blocks_per_chunk; ++i)
+ (void) r.allocate(block_size, 1);
+ // Should have filled the maximally-sized chunk and allocated another
+ // maximally-sized chunk from upstream:
+ VERIFY( c.reached_max );
+}
+
+int
+main()
+{
+ test01();
+}
