ladybird/Userland/DevTools/UserspaceEmulator/MallocTracer.cpp

/*
 * Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "MallocTracer.h"
#include "Emulator.h"
#include "MmapRegion.h"
#include <AK/Debug.h>
#include <AK/TemporaryChange.h>
#include <mallocdefs.h>
#include <string.h>
#include <unistd.h>

namespace UserspaceEmulator {

MallocTracer::MallocTracer(Emulator& emulator)
    : m_emulator(emulator)
{
}

template<typename Callback>
inline void MallocTracer::for_each_mallocation(Callback callback) const
{
    m_emulator.mmu().for_each_region([&](auto& region) {
        if (is<MmapRegion>(region) && static_cast<const MmapRegion&>(region).is_malloc_block()) {
            auto* malloc_data = static_cast<MmapRegion&>(region).malloc_metadata();
            for (auto& mallocation : malloc_data->mallocations) {
                if (mallocation.used && callback(mallocation) == IterationDecision::Break)
                    return IterationDecision::Break;
            }
        }
        return IterationDecision::Continue;
    });
}

void MallocTracer::target_did_malloc(Badge<Emulator>, FlatPtr address, size_t size)
{
    if (m_emulator.is_in_loader_code())
        return;
    auto* region = m_emulator.mmu().find_region({ 0x23, address });
    VERIFY(region);
    VERIFY(is<MmapRegion>(*region));
    auto& mmap_region = static_cast<MmapRegion&>(*region);

    auto* shadow_bits = mmap_region.shadow_data() + address - mmap_region.base();
    memset(shadow_bits, 0, size);

    if (auto* existing_mallocation = find_mallocation(address)) {
        VERIFY(existing_mallocation->freed);
        existing_mallocation->size = size;
        existing_mallocation->freed = false;
        existing_mallocation->malloc_backtrace = m_emulator.raw_backtrace();
        existing_mallocation->free_backtrace.clear();
        return;
    }

    if (!mmap_region.is_malloc_block()) {
        auto chunk_size = mmap_region.read32(offsetof(CommonHeader, m_size)).value();
        mmap_region.set_malloc_metadata({},
            adopt_own(*new MallocRegionMetadata {
                .region = mmap_region,
                .address = mmap_region.base(),
                .chunk_size = chunk_size,
                .mallocations = {},
            }));
        auto& malloc_data = *mmap_region.malloc_metadata();

        bool is_chunked_block = malloc_data.chunk_size <= size_classes[num_size_classes - 1];
        if (is_chunked_block)
            malloc_data.mallocations.resize((ChunkedBlock::block_size - sizeof(ChunkedBlock)) / malloc_data.chunk_size);
        else
            malloc_data.mallocations.resize(1);

        // Mark the containing mmap region as a malloc block!
        mmap_region.set_malloc(true);
    }
    auto* mallocation = mmap_region.malloc_metadata()->mallocation_for_address(address);
    VERIFY(mallocation);
    *mallocation = { address, size, true, false, m_emulator.raw_backtrace(), Vector<FlatPtr>() };
}

ALWAYS_INLINE Mallocation* MallocRegionMetadata::mallocation_for_address(FlatPtr address) const
{
    auto index = chunk_index_for_address(address);
    if (!index.has_value())
        return nullptr;
    return &const_cast<Mallocation&>(this->mallocations[index.value()]);
}

ALWAYS_INLINE Optional<size_t> MallocRegionMetadata::chunk_index_for_address(FlatPtr address) const
{
    bool is_chunked_block = chunk_size <= size_classes[num_size_classes - 1];
    if (!is_chunked_block) {
        // This is a BigAllocationBlock
        return 0;
    }
    auto offset_into_block = address - this->address;
    if (offset_into_block < sizeof(ChunkedBlock))
        return 0;
    auto chunk_offset = offset_into_block - sizeof(ChunkedBlock);
    auto chunk_index = chunk_offset / this->chunk_size;
    if (chunk_index >= mallocations.size())
        return {};
    return chunk_index;
}

void MallocTracer::target_did_free(Badge<Emulator>, FlatPtr address)
{
    if (!address)
        return;
    if (m_emulator.is_in_loader_code())
        return;

    if (auto* mallocation = find_mallocation(address)) {
        if (mallocation->freed) {
            reportln("\n=={}==  \033[31;1mDouble free()\033[0m, {:p}", getpid(), address);
            reportln("=={}==  Address {} has already been passed to free()", getpid(), address);
            m_emulator.dump_backtrace();
        } else {
            mallocation->freed = true;
            mallocation->free_backtrace = m_emulator.raw_backtrace();
        }
        return;
    }

    reportln("\n=={}==  \033[31;1mInvalid free()\033[0m, {:p}", getpid(), address);
    reportln("=={}==  Address {} has never been returned by malloc()", getpid(), address);
    m_emulator.dump_backtrace();
}

void MallocTracer::target_did_realloc(Badge<Emulator>, FlatPtr address, size_t size)
{
    if (m_emulator.is_in_loader_code())
        return;
    auto* region = m_emulator.mmu().find_region({ 0x23, address });
    VERIFY(region);
    VERIFY(is<MmapRegion>(*region));
    auto& mmap_region = static_cast<MmapRegion&>(*region);

    VERIFY(mmap_region.is_malloc_block());

    auto* existing_mallocation = find_mallocation(address);
    VERIFY(existing_mallocation);
    VERIFY(!existing_mallocation->freed);

    size_t old_size = existing_mallocation->size;

    auto* shadow_bits = mmap_region.shadow_data() + address - mmap_region.base();

    if (size > old_size) {
        memset(shadow_bits + old_size, 1, size - old_size);
    } else {
        memset(shadow_bits + size, 1, old_size - size);
    }

    existing_mallocation->size = size;
    // FIXME: Should we track malloc/realloc backtrace separately perhaps?
    existing_mallocation->malloc_backtrace = m_emulator.raw_backtrace();
}

Mallocation* MallocTracer::find_mallocation(FlatPtr address)
{
    auto* region = m_emulator.mmu().find_region({ 0x23, address });
    if (!region)
        return nullptr;
    return find_mallocation(*region, address);
}

Mallocation* MallocTracer::find_mallocation_before(FlatPtr address)
{
    Mallocation* found_mallocation = nullptr;
    for_each_mallocation([&](auto& mallocation) {
        if (mallocation.address >= address)
            return IterationDecision::Continue;
        if (!found_mallocation || (mallocation.address > found_mallocation->address))
            found_mallocation = const_cast<Mallocation*>(&mallocation);
        return IterationDecision::Continue;
    });
    return found_mallocation;
}

Mallocation* MallocTracer::find_mallocation_after(FlatPtr address)
{
    Mallocation* found_mallocation = nullptr;
    for_each_mallocation([&](auto& mallocation) {
        if (mallocation.address <= address)
            return IterationDecision::Continue;
        if (!found_mallocation || (mallocation.address < found_mallocation->address))
            found_mallocation = const_cast<Mallocation*>(&mallocation);
        return IterationDecision::Continue;
    });
    return found_mallocation;
}

void MallocTracer::audit_read(const Region& region, FlatPtr address, size_t size)
{
    if (!m_auditing_enabled)
        return;

    if (m_emulator.is_in_malloc_or_free() || m_emulator.is_in_libsystem()) {
        return;
    }

    if (m_emulator.is_in_loader_code()) {
        return;
    }

    auto* mallocation = find_mallocation(region, address);

    if (!mallocation) {
        reportln("\n=={}==  \033[31;1mHeap buffer overflow\033[0m, invalid {}-byte read at address {:p}", getpid(), size, address);
        m_emulator.dump_backtrace();
        auto* mallocation_before = find_mallocation_before(address);
        auto* mallocation_after = find_mallocation_after(address);
        size_t distance_to_mallocation_before = mallocation_before ? (address - mallocation_before->address - mallocation_before->size) : 0;
        size_t distance_to_mallocation_after = mallocation_after ? (mallocation_after->address - address) : 0;
        if (mallocation_before && (!mallocation_after || distance_to_mallocation_before < distance_to_mallocation_after)) {
            reportln("=={}==  Address is {} byte(s) after block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_before, mallocation_before->size, mallocation_before->address);
            m_emulator.dump_backtrace(mallocation_before->malloc_backtrace);
            return;
        }
        if (mallocation_after && (!mallocation_before || distance_to_mallocation_after < distance_to_mallocation_before)) {
            reportln("=={}==  Address is {} byte(s) before block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_after, mallocation_after->size, mallocation_after->address);
            m_emulator.dump_backtrace(mallocation_after->malloc_backtrace);
        }
        return;
    }

    size_t offset_into_mallocation = address - mallocation->address;

    if (mallocation->freed) {
        reportln("\n=={}==  \033[31;1mUse-after-free\033[0m, invalid {}-byte read at address {:p}", getpid(), size, address);
        m_emulator.dump_backtrace();
        reportln("=={}==  Address is {} byte(s) into block of size {}, allocated at:", getpid(), offset_into_mallocation, mallocation->size);
        m_emulator.dump_backtrace(mallocation->malloc_backtrace);
        reportln("=={}==  Later freed at:", getpid());
        m_emulator.dump_backtrace(mallocation->free_backtrace);
        return;
    }
}

void MallocTracer::audit_write(const Region& region, FlatPtr address, size_t size)
{
    if (!m_auditing_enabled)
        return;

    if (m_emulator.is_in_malloc_or_free())
        return;

    if (m_emulator.is_in_loader_code()) {
        return;
    }

    auto* mallocation = find_mallocation(region, address);
    if (!mallocation) {
        reportln("\n=={}==  \033[31;1mHeap buffer overflow\033[0m, invalid {}-byte write at address {:p}", getpid(), size, address);
        m_emulator.dump_backtrace();
        auto* mallocation_before = find_mallocation_before(address);
        auto* mallocation_after = find_mallocation_after(address);
        size_t distance_to_mallocation_before = mallocation_before ? (address - mallocation_before->address - mallocation_before->size) : 0;
        size_t distance_to_mallocation_after = mallocation_after ? (mallocation_after->address - address) : 0;
        if (mallocation_before && (!mallocation_after || distance_to_mallocation_before < distance_to_mallocation_after)) {
            reportln("=={}==  Address is {} byte(s) after block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_before, mallocation_before->size, mallocation_before->address);
            m_emulator.dump_backtrace(mallocation_before->malloc_backtrace);
            return;
        }
        if (mallocation_after && (!mallocation_before || distance_to_mallocation_after < distance_to_mallocation_before)) {
            reportln("=={}==  Address is {} byte(s) before block of size {}, identity {:p}, allocated at:", getpid(), distance_to_mallocation_after, mallocation_after->size, mallocation_after->address);
            m_emulator.dump_backtrace(mallocation_after->malloc_backtrace);
        }
        return;
    }

    size_t offset_into_mallocation = address - mallocation->address;

    if (mallocation->freed) {
        reportln("\n=={}==  \033[31;1mUse-after-free\033[0m, invalid {}-byte write at address {:p}", getpid(), size, address);
        m_emulator.dump_backtrace();
        reportln("=={}==  Address is {} byte(s) into block of size {}, allocated at:", getpid(), offset_into_mallocation, mallocation->size);
        m_emulator.dump_backtrace(mallocation->malloc_backtrace);
        reportln("=={}==  Later freed at:", getpid());
        m_emulator.dump_backtrace(mallocation->free_backtrace);
        return;
    }
}

bool MallocTracer::is_reachable(const Mallocation& mallocation) const
{
    VERIFY(!mallocation.freed);

    bool reachable = false;

    // 1. Search in active (non-freed) mallocations for pointers to this mallocation
    for_each_mallocation([&](auto& other_mallocation) {
        if (&mallocation == &other_mallocation)
            return IterationDecision::Continue;
        if (other_mallocation.freed)
            return IterationDecision::Continue;
        size_t pointers_in_mallocation = other_mallocation.size / sizeof(u32);
        for (size_t i = 0; i < pointers_in_mallocation; ++i) {
            auto value = m_emulator.mmu().read32({ 0x23, other_mallocation.address + i * sizeof(u32) });
            if (value.value() == mallocation.address && !value.is_uninitialized()) {
#if REACHABLE_DEBUG
                reportln("mallocation {:p} is reachable from other mallocation {:p}", mallocation.address, other_mallocation.address);
#endif
                reachable = true;
                return IterationDecision::Break;
            }
        }
        return IterationDecision::Continue;
    });

    if (reachable)
        return true;

    // 2. Search in other memory regions for pointers to this mallocation
    m_emulator.mmu().for_each_region([&](auto& region) {
        // Skip the stack
        if (region.is_stack())
            return IterationDecision::Continue;
        if (region.is_text())
            return IterationDecision::Continue;
        if (!region.is_readable())
            return IterationDecision::Continue;
        // Skip malloc blocks
        if (is<MmapRegion>(region) && static_cast<const MmapRegion&>(region).is_malloc_block())
            return IterationDecision::Continue;

        size_t pointers_in_region = region.size() / sizeof(u32);
        for (size_t i = 0; i < pointers_in_region; ++i) {
            auto value = region.read32(i * sizeof(u32));
            if (value.value() == mallocation.address && !value.is_uninitialized()) {
#if REACHABLE_DEBUG
                reportln("mallocation {:p} is reachable from region {:p}-{:p}", mallocation.address, region.base(), region.end() - 1);
#endif
                reachable = true;
                return IterationDecision::Break;
            }
        }
        return IterationDecision::Continue;
    });
    return reachable;
}

void MallocTracer::dump_leak_report()
{
    TemporaryChange change(m_auditing_enabled, false);

    size_t bytes_leaked = 0;
    size_t leaks_found = 0;
    for_each_mallocation([&](auto& mallocation) {
        if (mallocation.freed)
            return IterationDecision::Continue;
        if (is_reachable(mallocation))
            return IterationDecision::Continue;
        ++leaks_found;
        bytes_leaked += mallocation.size;
        reportln("\n=={}==  \033[31;1mLeak\033[0m, {}-byte allocation at address {:p}", getpid(), mallocation.size, mallocation.address);
        m_emulator.dump_backtrace(mallocation.malloc_backtrace);
        return IterationDecision::Continue;
    });

    if (!leaks_found)
        reportln("\n=={}==  \033[32;1mNo leaks found!\033[0m", getpid());
    else
        reportln("\n=={}==  \033[31;1m{} leak(s) found: {} byte(s) leaked\033[0m", getpid(), leaks_found, bytes_leaked);
}

}