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https://github.com/RGBCube/serenity
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2fceffff6f
Instead of doing an O(n) scan over all the mallocations whenever we're doing a read/write audit, UE now keeps track of ChunkedBlocks and their chunks. Both the block lookup and the chunk lookup is O(1). We know what ChunkedBlocks look like via mallocdefs.h from LibC. Note that the old linear scan is still in use for big mallocations, but the vast majority of mallocations are chunked, so this helps a lot. This makes malloc auditing significantly faster! :^)
353 lines
15 KiB
C++
353 lines
15 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "MallocTracer.h"
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#include "Emulator.h"
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#include "MmapRegion.h"
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#include <AK/LogStream.h>
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#include <AK/TemporaryChange.h>
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#include <mallocdefs.h>
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#include <string.h>
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//#define REACHABLE_DEBUG
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namespace UserspaceEmulator {
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MallocTracer::MallocTracer()
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{
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}
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void MallocTracer::target_did_malloc(Badge<SoftCPU>, FlatPtr address, size_t size)
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{
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auto* region = Emulator::the().mmu().find_region({ 0x20, address });
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ASSERT(region);
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ASSERT(region->is_mmap());
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auto& mmap_region = static_cast<MmapRegion&>(*region);
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// Mark the containing mmap region as a malloc block!
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mmap_region.set_malloc(true);
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auto* shadow_bits = mmap_region.shadow_data() + address - mmap_region.base();
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memset(shadow_bits, 0, size);
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if (auto* existing_mallocation = find_mallocation(address)) {
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ASSERT(existing_mallocation->freed);
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existing_mallocation->size = size;
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existing_mallocation->freed = false;
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existing_mallocation->malloc_backtrace = Emulator::the().raw_backtrace();
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existing_mallocation->free_backtrace.clear();
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return;
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}
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if (size <= size_classes[num_size_classes - 1]) {
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FlatPtr chunked_block_address = address & ChunkedBlock::block_mask;
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// FIXME: Don't do a double hash lookup here.
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auto tracked_chunked_block = m_chunked_blocks.get(chunked_block_address);
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if (!tracked_chunked_block.has_value()) {
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m_chunked_blocks.set(chunked_block_address, make<TrackedChunkedBlock>());
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tracked_chunked_block = m_chunked_blocks.get(chunked_block_address);
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auto& block = const_cast<TrackedChunkedBlock&>(*tracked_chunked_block.value());
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block.address = chunked_block_address;
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block.chunk_size = mmap_region.read32(offsetof(CommonHeader, m_size)).value();
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auto chunk_count = (ChunkedBlock::block_size - sizeof(ChunkedBlock)) / block.chunk_size;
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block.mallocations.resize(chunk_count);
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dbgln("Tracking ChunkedBlock @ {:p} with chunk_size={}, chunk_count={}", block.address, block.chunk_size, chunk_count);
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}
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ASSERT(tracked_chunked_block.has_value());
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auto& block = const_cast<TrackedChunkedBlock&>(*tracked_chunked_block.value());
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auto chunk_offset = address - (block.address + sizeof(ChunkedBlock));
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auto chunk_index = chunk_offset / block.chunk_size;
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block.mallocations[chunk_index] = { address, size, true, false, Emulator::the().raw_backtrace(), Vector<FlatPtr>() };
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} else {
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m_big_mallocations.append({ address, size, true, false, Emulator::the().raw_backtrace(), Vector<FlatPtr>() });
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}
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}
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void MallocTracer::target_did_free(Badge<SoftCPU>, FlatPtr address)
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{
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if (!address)
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return;
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if (auto* mallocation = find_mallocation(address)) {
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if (mallocation->freed) {
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reportln("\n=={}== \033[31;1mDouble free()\033[0m, {:p}", getpid(), address);
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reportln("=={}== Address {} has already been passed to free()", getpid(), address);
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Emulator::the().dump_backtrace();
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} else {
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mallocation->freed = true;
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mallocation->free_backtrace = Emulator::the().raw_backtrace();
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}
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return;
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}
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reportln("\n=={}== \033[31;1mInvalid free()\033[0m, {:p}", getpid(), address);
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reportln("=={}== Address {} has never been returned by malloc()", getpid(), address);
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Emulator::the().dump_backtrace();
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}
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void MallocTracer::target_did_realloc(Badge<SoftCPU>, FlatPtr address, size_t size)
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{
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auto* region = Emulator::the().mmu().find_region({ 0x20, address });
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ASSERT(region);
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ASSERT(region->is_mmap());
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auto& mmap_region = static_cast<MmapRegion&>(*region);
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ASSERT(mmap_region.is_malloc_block());
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auto* existing_mallocation = find_mallocation(address);
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ASSERT(existing_mallocation);
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ASSERT(!existing_mallocation->freed);
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size_t old_size = existing_mallocation->size;
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auto* shadow_bits = mmap_region.shadow_data() + address - mmap_region.base();
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if (size > old_size) {
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memset(shadow_bits + old_size, 1, size - old_size);
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} else {
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memset(shadow_bits + size, 1, old_size - size);
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}
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existing_mallocation->size = size;
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// FIXME: Should we track malloc/realloc backtrace separately perhaps?
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existing_mallocation->malloc_backtrace = Emulator::the().raw_backtrace();
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}
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MallocTracer::Mallocation* MallocTracer::find_mallocation(FlatPtr address)
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{
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FlatPtr possible_chunked_block = address & ChunkedBlock::block_mask;
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auto chunked_block = m_chunked_blocks.get(possible_chunked_block);
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if (chunked_block.has_value()) {
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auto& block = *chunked_block.value();
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auto chunk_offset = address - (block.address + sizeof(ChunkedBlock));
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auto chunk_index = chunk_offset / block.chunk_size;
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auto& mallocation = block.mallocations[chunk_index];
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if (mallocation.used) {
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ASSERT(mallocation.contains(address));
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return const_cast<Mallocation*>(&mallocation);
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}
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return nullptr;
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}
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for (auto& mallocation : m_big_mallocations) {
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if (mallocation.contains(address))
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return &mallocation;
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}
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return nullptr;
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}
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MallocTracer::Mallocation* MallocTracer::find_mallocation_before(FlatPtr address)
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{
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Mallocation* found_mallocation = nullptr;
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for_each_mallocation([&](auto& mallocation) {
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if (mallocation.address >= address)
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return IterationDecision::Continue;
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if (!found_mallocation || (mallocation.address > found_mallocation->address))
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found_mallocation = const_cast<Mallocation*>(&mallocation);
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return IterationDecision::Continue;
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});
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return found_mallocation;
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}
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MallocTracer::Mallocation* MallocTracer::find_mallocation_after(FlatPtr address)
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{
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Mallocation* found_mallocation = nullptr;
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for_each_mallocation([&](auto& mallocation) {
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if (mallocation.address <= address)
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return IterationDecision::Continue;
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if (!found_mallocation || (mallocation.address < found_mallocation->address))
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found_mallocation = const_cast<Mallocation*>(&mallocation);
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return IterationDecision::Continue;
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});
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return found_mallocation;
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}
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void MallocTracer::audit_read(FlatPtr address, size_t size)
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{
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if (!m_auditing_enabled)
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return;
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if (Emulator::the().is_in_malloc_or_free())
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return;
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auto* mallocation = find_mallocation(address);
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if (!mallocation) {
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reportln("\n=={}== \033[31;1mHeap buffer overflow\033[0m, invalid {}-byte read at address {:p}", getpid(), size, address);
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Emulator::the().dump_backtrace();
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auto* mallocation_before = find_mallocation_before(address);
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auto* mallocation_after = find_mallocation_after(address);
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size_t distance_to_mallocation_before = mallocation_before ? (address - mallocation_before->address - mallocation_before->size) : 0;
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size_t distance_to_mallocation_after = mallocation_after ? (mallocation_after->address - address) : 0;
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if (mallocation_before && (!mallocation_after || distance_to_mallocation_before < distance_to_mallocation_after)) {
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reportln("=={}== Address is {} byte(s) after block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_before, mallocation_before->size, mallocation_before->address);
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Emulator::the().dump_backtrace(mallocation_before->malloc_backtrace);
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return;
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}
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if (mallocation_after && (!mallocation_before || distance_to_mallocation_after < distance_to_mallocation_before)) {
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reportln("=={}== Address is {} byte(s) before block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_after, mallocation_after->size, mallocation_after->address);
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Emulator::the().dump_backtrace(mallocation_after->malloc_backtrace);
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}
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return;
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}
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size_t offset_into_mallocation = address - mallocation->address;
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if (mallocation->freed) {
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reportln("\n=={}== \033[31;1mUse-after-free\033[0m, invalid {}-byte read at address {:p}", getpid(), size, address);
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Emulator::the().dump_backtrace();
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reportln("=={}== Address is {} byte(s) into block of size {}, allocated at:", getpid(), offset_into_mallocation, mallocation->size);
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Emulator::the().dump_backtrace(mallocation->malloc_backtrace);
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reportln("=={}== Later freed at:", getpid());
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Emulator::the().dump_backtrace(mallocation->free_backtrace);
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return;
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}
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}
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void MallocTracer::audit_write(FlatPtr address, size_t size)
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{
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if (!m_auditing_enabled)
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return;
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if (Emulator::the().is_in_malloc_or_free())
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return;
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auto* mallocation = find_mallocation(address);
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if (!mallocation) {
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reportln("\n=={}== \033[31;1mHeap buffer overflow\033[0m, invalid {}-byte write at address {:p}", getpid(), size, address);
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Emulator::the().dump_backtrace();
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auto* mallocation_before = find_mallocation_before(address);
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auto* mallocation_after = find_mallocation_after(address);
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size_t distance_to_mallocation_before = mallocation_before ? (address - mallocation_before->address - mallocation_before->size) : 0;
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size_t distance_to_mallocation_after = mallocation_after ? (mallocation_after->address - address) : 0;
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if (mallocation_before && (!mallocation_after || distance_to_mallocation_before < distance_to_mallocation_after)) {
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reportln("=={}== Address is {} byte(s) after block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_before, mallocation_before->size, mallocation_before->address);
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Emulator::the().dump_backtrace(mallocation_before->malloc_backtrace);
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return;
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}
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if (mallocation_after && (!mallocation_before || distance_to_mallocation_after < distance_to_mallocation_before)) {
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reportln("=={}== Address is {} byte(s) before block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_after, mallocation_after->size, mallocation_after->address);
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Emulator::the().dump_backtrace(mallocation_after->malloc_backtrace);
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}
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return;
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}
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size_t offset_into_mallocation = address - mallocation->address;
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if (mallocation->freed) {
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reportln("\n=={}== \033[31;1mUse-after-free\033[0m, invalid {}-byte write at address {:p}", getpid(), size, address);
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Emulator::the().dump_backtrace();
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reportln("=={}== Address is {} byte(s) into block of size {}, allocated at:", getpid(), offset_into_mallocation, mallocation->size);
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Emulator::the().dump_backtrace(mallocation->malloc_backtrace);
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reportln("=={}== Later freed at:", getpid());
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Emulator::the().dump_backtrace(mallocation->free_backtrace);
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return;
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}
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}
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bool MallocTracer::is_reachable(const Mallocation& mallocation) const
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{
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ASSERT(!mallocation.freed);
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bool reachable = false;
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// 1. Search in active (non-freed) mallocations for pointers to this mallocation
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for_each_mallocation([&](auto& other_mallocation) {
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if (&mallocation == &other_mallocation)
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return IterationDecision::Continue;
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if (other_mallocation.freed)
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return IterationDecision::Continue;
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size_t pointers_in_mallocation = other_mallocation.size / sizeof(u32);
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for (size_t i = 0; i < pointers_in_mallocation; ++i) {
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auto value = Emulator::the().mmu().read32({ 0x20, other_mallocation.address + i * sizeof(u32) });
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if (value.value() == mallocation.address && !value.is_uninitialized()) {
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#ifdef REACHABLE_DEBUG
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reportln("mallocation {:p} is reachable from other mallocation {:p}", mallocation.address, other_mallocation.address);
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#endif
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reachable = true;
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return IterationDecision::Break;
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}
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}
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return IterationDecision::Continue;
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});
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if (reachable)
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return true;
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// 2. Search in other memory regions for pointers to this mallocation
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Emulator::the().mmu().for_each_region([&](auto& region) {
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// Skip the stack
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if (region.is_stack())
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return IterationDecision::Continue;
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if (region.is_text())
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return IterationDecision::Continue;
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// Skip malloc blocks
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if (region.is_mmap() && static_cast<const MmapRegion&>(region).is_malloc_block())
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return IterationDecision::Continue;
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size_t pointers_in_region = region.size() / sizeof(u32);
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for (size_t i = 0; i < pointers_in_region; ++i) {
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auto value = region.read32(i * sizeof(u32));
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if (value.value() == mallocation.address && !value.is_uninitialized()) {
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#ifdef REACHABLE_DEBUG
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reportln("mallocation {:p} is reachable from region {:p}-{:p}", mallocation.address, region.base(), region.end() - 1);
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#endif
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reachable = true;
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return IterationDecision::Break;
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}
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}
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return IterationDecision::Continue;
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});
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return reachable;
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}
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void MallocTracer::dump_leak_report()
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{
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TemporaryChange change(m_auditing_enabled, false);
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size_t bytes_leaked = 0;
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size_t leaks_found = 0;
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for_each_mallocation([&](auto& mallocation) {
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if (mallocation.freed)
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return IterationDecision::Continue;
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if (is_reachable(mallocation))
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return IterationDecision::Continue;
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++leaks_found;
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bytes_leaked += mallocation.size;
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reportln("\n=={}== \033[31;1mLeak\033[0m, {}-byte allocation at address {:p}", getpid(), mallocation.size, mallocation.address);
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Emulator::the().dump_backtrace(mallocation.malloc_backtrace);
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return IterationDecision::Continue;
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});
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if (!leaks_found)
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reportln("\n=={}== \033[32;1mNo leaks found!\033[0m", getpid());
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else
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reportln("\n=={}== \033[31;1m{} leak(s) found: {} byte(s) leaked\033[0m", getpid(), leaks_found, bytes_leaked);
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}
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}
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