PoolAlloc.cpp

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Author : Jamie Madill
Date : 2016-06-17 14:20:05
Hash : 438dbcf1
Message : translator: Fix builtin function emulator use-after-free. We were calling the global pool allocator in the builtin function emulator, which would lead to us freeing TTypes that were still referenced. Fix this by using the TCache which was designed for such a purpose, and locking the allocator around the builtin function emulator to try and prevent similar bugs from creeping in. Eventually we would like to get rid of the global allocator and replace it with different pools in different contexts, which are managed more safely. BUG=620937 Change-Id: If501ff6ea4d9bf8a2b8f89f2c94a01386f79ee3a Reviewed-on: https://chromium-review.googlesource.com/353671 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>

src/compiler/translator/PoolAlloc.cpp

//
// Copyright (c) 2002-2010 The ANGLE Project Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//

#include "compiler/translator/PoolAlloc.h"

#include <stdint.h>
#include <stdio.h>
#include <assert.h>

#include "common/angleutils.h"
#include "common/debug.h"
#include "common/platform.h"
#include "common/tls.h"
#include "compiler/translator/InitializeGlobals.h"

TLSIndex PoolIndex = TLS_INVALID_INDEX;

bool InitializePoolIndex()
{
    assert(PoolIndex == TLS_INVALID_INDEX);

    PoolIndex = CreateTLSIndex();
    return PoolIndex != TLS_INVALID_INDEX;
}

void FreePoolIndex()
{
    assert(PoolIndex != TLS_INVALID_INDEX);

    DestroyTLSIndex(PoolIndex);
    PoolIndex = TLS_INVALID_INDEX;
}

TPoolAllocator* GetGlobalPoolAllocator()
{
    assert(PoolIndex != TLS_INVALID_INDEX);
    return static_cast<TPoolAllocator*>(GetTLSValue(PoolIndex));
}

void SetGlobalPoolAllocator(TPoolAllocator* poolAllocator)
{
    assert(PoolIndex != TLS_INVALID_INDEX);
    SetTLSValue(PoolIndex, poolAllocator);
}

//
// Implement the functionality of the TPoolAllocator class, which
// is documented in PoolAlloc.h.
//
TPoolAllocator::TPoolAllocator(int growthIncrement, int allocationAlignment) : 
    pageSize(growthIncrement),
    alignment(allocationAlignment),
    freeList(0),
    inUseList(0),
    numCalls(0),
    totalBytes(0),
    mLocked(false)
{
    //
    // Don't allow page sizes we know are smaller than all common
    // OS page sizes.
    //
    if (pageSize < 4*1024)
        pageSize = 4*1024;

    //
    // A large currentPageOffset indicates a new page needs to
    // be obtained to allocate memory.
    //
    currentPageOffset = pageSize;

    //
    // Adjust alignment to be at least pointer aligned and
    // power of 2.
    //
    size_t minAlign = sizeof(void*);
    alignment &= ~(minAlign - 1);
    if (alignment < minAlign)
        alignment = minAlign;
    size_t a = 1;
    while (a < alignment)
        a <<= 1;
    alignment = a;
    alignmentMask = a - 1;

    //
    // Align header skip
    //
    headerSkip = minAlign;
    if (headerSkip < sizeof(tHeader)) {
        headerSkip = (sizeof(tHeader) + alignmentMask) & ~alignmentMask;
    }
}

TPoolAllocator::~TPoolAllocator()
{
    while (inUseList) {
        tHeader* next = inUseList->nextPage;
        inUseList->~tHeader();
        delete [] reinterpret_cast<char*>(inUseList);
        inUseList = next;
    }

    // We should not check the guard blocks
    // here, because we did it already when the block was
    // placed into the free list.
    //
    while (freeList) {
        tHeader* next = freeList->nextPage;
        delete [] reinterpret_cast<char*>(freeList);
        freeList = next;
    }
}

// Support MSVC++ 6.0
const unsigned char TAllocation::guardBlockBeginVal = 0xfb;
const unsigned char TAllocation::guardBlockEndVal   = 0xfe;
const unsigned char TAllocation::userDataFill       = 0xcd;

#ifdef GUARD_BLOCKS
    const size_t TAllocation::guardBlockSize = 16;
#else
    const size_t TAllocation::guardBlockSize = 0;
#endif

//
// Check a single guard block for damage
//
void TAllocation::checkGuardBlock(unsigned char* blockMem, unsigned char val, const char* locText) const
{
#ifdef GUARD_BLOCKS
    for (size_t x = 0; x < guardBlockSize; x++) {
        if (blockMem[x] != val) {
            char assertMsg[80];

            // We don't print the assert message.  It's here just to be helpful.
#if defined(_MSC_VER)
            snprintf(assertMsg, sizeof(assertMsg), "PoolAlloc: Damage %s %Iu byte allocation at 0x%p\n",
                    locText, size, data());
#else
            snprintf(assertMsg, sizeof(assertMsg), "PoolAlloc: Damage %s %zu byte allocation at 0x%p\n",
                    locText, size, data());
#endif
            assert(0 && "PoolAlloc: Damage in guard block");
        }
    }
#endif
}


void TPoolAllocator::push()
{
    tAllocState state = { currentPageOffset, inUseList };

    stack.push_back(state);
        
    //
    // Indicate there is no current page to allocate from.
    //
    currentPageOffset = pageSize;
}

//
// Do a mass-deallocation of all the individual allocations
// that have occurred since the last push(), or since the
// last pop(), or since the object's creation.
//
// The deallocated pages are saved for future allocations.
//
void TPoolAllocator::pop()
{
    if (stack.size() < 1)
        return;

    tHeader* page = stack.back().page;
    currentPageOffset = stack.back().offset;

    while (inUseList != page) {
        // invoke destructor to free allocation list
        inUseList->~tHeader();
        
        tHeader* nextInUse = inUseList->nextPage;
        if (inUseList->pageCount > 1)
            delete [] reinterpret_cast<char*>(inUseList);
        else {
            inUseList->nextPage = freeList;
            freeList = inUseList;
        }
        inUseList = nextInUse;
    }

    stack.pop_back();
}

//
// Do a mass-deallocation of all the individual allocations
// that have occurred.
//
void TPoolAllocator::popAll()
{
    while (stack.size() > 0)
        pop();
}

void* TPoolAllocator::allocate(size_t numBytes)
{
    ASSERT(!mLocked);

    //
    // Just keep some interesting statistics.
    //
    ++numCalls;
    totalBytes += numBytes;

    // If we are using guard blocks, all allocations are bracketed by
    // them: [guardblock][allocation][guardblock].  numBytes is how
    // much memory the caller asked for.  allocationSize is the total
    // size including guard blocks.  In release build,
    // guardBlockSize=0 and this all gets optimized away.
    size_t allocationSize = TAllocation::allocationSize(numBytes);
    // Detect integer overflow.
    if (allocationSize < numBytes)
        return 0;

    //
    // Do the allocation, most likely case first, for efficiency.
    // This step could be moved to be inline sometime.
    //
    if (allocationSize <= pageSize - currentPageOffset) {
        //
        // Safe to allocate from currentPageOffset.
        //
        unsigned char* memory = reinterpret_cast<unsigned char *>(inUseList) + currentPageOffset;
        currentPageOffset += allocationSize;
        currentPageOffset = (currentPageOffset + alignmentMask) & ~alignmentMask;

        return initializeAllocation(inUseList, memory, numBytes);
    }

    if (allocationSize > pageSize - headerSkip) {
        //
        // Do a multi-page allocation.  Don't mix these with the others.
        // The OS is efficient and allocating and free-ing multiple pages.
        //
        size_t numBytesToAlloc = allocationSize + headerSkip;
        // Detect integer overflow.
        if (numBytesToAlloc < allocationSize)
            return 0;

        tHeader* memory = reinterpret_cast<tHeader*>(::new char[numBytesToAlloc]);
        if (memory == 0)
            return 0;

        // Use placement-new to initialize header
        new(memory) tHeader(inUseList, (numBytesToAlloc + pageSize - 1) / pageSize);
        inUseList = memory;

        currentPageOffset = pageSize;  // make next allocation come from a new page

        // No guard blocks for multi-page allocations (yet)
        return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(memory) + headerSkip);
    }

    //
    // Need a simple page to allocate from.
    //
    tHeader* memory;
    if (freeList) {
        memory = freeList;
        freeList = freeList->nextPage;
    } else {
        memory = reinterpret_cast<tHeader*>(::new char[pageSize]);
        if (memory == 0)
            return 0;
    }

    // Use placement-new to initialize header
    new(memory) tHeader(inUseList, 1);
    inUseList = memory;
    
    unsigned char* ret = reinterpret_cast<unsigned char *>(inUseList) + headerSkip;
    currentPageOffset = (headerSkip + allocationSize + alignmentMask) & ~alignmentMask;

    return initializeAllocation(inUseList, ret, numBytes);
}

void TPoolAllocator::lock()
{
    ASSERT(!mLocked);
    mLocked = true;
}

void TPoolAllocator::unlock()
{
    ASSERT(mLocked);
    mLocked = false;
}

//
// Check all allocations in a list for damage by calling check on each.
//
void TAllocation::checkAllocList() const
{
    for (const TAllocation* alloc = this; alloc != 0; alloc = alloc->prevAlloc)
        alloc->check();
}

kc3-lang/angle/src/compiler/translator/PoolAlloc.cpp

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kc3-lang/angle /src/compiler/translator/PoolAlloc.cpp