sravan/system76-edk2
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

MdeModulePkg/Core: add freed-memory guard feature

Browse Source 
Freed-memory guard is used to detect UAF (Use-After-Free) memory issue
which is illegal access to memory which has been freed. The principle
behind is similar to pool guard feature, that is we'll turn all pool
memory allocation to page allocation and mark them to be not-present
once they are freed.

This also implies that, once a page is allocated and freed, it cannot
be re-allocated. This will bring another issue, which is that there's
risk that memory space will be used out. To address it, the memory
service add logic to put part (at most 64 pages a time) of freed pages
back into page pool, so that the memory service can still have memory
to allocate, when all memory space have been allocated once. This is
called memory promotion. The promoted pages are always from the eldest
pages which haven been freed.

This feature brings another problem is that memory map descriptors will
be increased enormously (200+ -> 2000+). One of change in this patch
is to update MergeMemoryMap() in file PropertiesTable.c to allow merge
freed pages back into the memory map. Now the number can stay at around
510.

Cc: Star Zeng <star.zeng@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
This commit is contained in:
Jian J Wang
2018-10-24 12:47:45 +08:00
parent bb685071c2
commit 63ebde8ef6
6 changed files with 525 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files

409
MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
View File

@@ -44,6 +44,11 @@ GLOBAL_REMOVE_IF_UNREFERENCED UINTN mLevelShift[GUARDED_HEAP_MAP_TABLE_DEPTH]
GLOBAL_REMOVE_IF_UNREFERENCED UINTN mLevelMask[GUARDED_HEAP_MAP_TABLE_DEPTH]
= GUARDED_HEAP_MAP_TABLE_DEPTH_MASKS;
//
// Used for promoting freed but not used pages.
//
GLOBAL_REMOVE_IF_UNREFERENCED EFI_PHYSICAL_ADDRESS mLastPromotedPage = BASE_4GB;
/**
Set corresponding bits in bitmap table to 1 according to the address.
@@ -379,7 +384,7 @@ ClearGuardedMemoryBits (
@return An integer containing the guarded memory bitmap.
**/
UINTN
UINT64
GetGuardedMemoryBits (
IN EFI_PHYSICAL_ADDRESS Address,
IN UINTN NumberOfPages
@@ -387,7 +392,7 @@ GetGuardedMemoryBits (
{
UINT64 *BitMap;
UINTN Bits;
UINTN Result;
UINT64 Result;
UINTN Shift;
UINTN BitsToUnitEnd;
@@ -660,15 +665,16 @@ IsPageTypeToGuard (
/**
Check to see if the heap guard is enabled for page and/or pool allocation.
@param[in] GuardType Specify the sub-type(s) of Heap Guard.
@return TRUE/FALSE.
**/
BOOLEAN
IsHeapGuardEnabled (
VOID
UINT8 GuardType
)
{
return IsMemoryTypeToGuard (EfiMaxMemoryType, AllocateAnyPages,
GUARD_HEAP_TYPE_POOL|GUARD_HEAP_TYPE_PAGE);
return IsMemoryTypeToGuard (EfiMaxMemoryType, AllocateAnyPages, GuardType);
}
/**
@@ -1203,6 +1209,380 @@ SetAllGuardPages (
}
}
/**
Find the address of top-most guarded free page.
@param[out] Address Start address of top-most guarded free page.
@return VOID.
**/
VOID
GetLastGuardedFreePageAddress (
OUT EFI_PHYSICAL_ADDRESS *Address
)
{
EFI_PHYSICAL_ADDRESS AddressGranularity;
EFI_PHYSICAL_ADDRESS BaseAddress;
UINTN Level;
UINT64 Map;
INTN Index;
ASSERT (mMapLevel >= 1);
BaseAddress = 0;
Map = mGuardedMemoryMap;
for (Level = GUARDED_HEAP_MAP_TABLE_DEPTH - mMapLevel;
Level < GUARDED_HEAP_MAP_TABLE_DEPTH;
++Level) {
AddressGranularity = LShiftU64 (1, mLevelShift[Level]);
//
// Find the non-NULL entry at largest index.
//
for (Index = (INTN)mLevelMask[Level]; Index >= 0 ; --Index) {
if (((UINT64 *)(UINTN)Map)[Index] != 0) {
BaseAddress += MultU64x32 (AddressGranularity, (UINT32)Index);
Map = ((UINT64 *)(UINTN)Map)[Index];
break;
}
}
}
//
// Find the non-zero MSB then get the page address.
//
while (Map != 0) {
Map = RShiftU64 (Map, 1);
BaseAddress += EFI_PAGES_TO_SIZE (1);
}
*Address = BaseAddress;
}
/**
Record freed pages.
@param[in] BaseAddress Base address of just freed pages.
@param[in] Pages Number of freed pages.
@return VOID.
**/
VOID
MarkFreedPages (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINTN Pages
)
{
SetGuardedMemoryBits (BaseAddress, Pages);
}
/**
Record freed pages as well as mark them as not-present.
@param[in] BaseAddress Base address of just freed pages.
@param[in] Pages Number of freed pages.
@return VOID.
**/
VOID
EFIAPI
GuardFreedPages (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINTN Pages
)
{
EFI_STATUS Status;
//
// Legacy memory lower than 1MB might be accessed with no allocation. Leave
// them alone.
//
if (BaseAddress < BASE_1MB) {
return;
}
MarkFreedPages (BaseAddress, Pages);
if (gCpu != NULL) {
//
// Set flag to make sure allocating memory without GUARD for page table
// operation; otherwise infinite loops could be caused.
//
mOnGuarding = TRUE;
//
// Note: This might overwrite other attributes needed by other features,
// such as NX memory protection.
//
Status = gCpu->SetMemoryAttributes (
gCpu,
BaseAddress,
EFI_PAGES_TO_SIZE (Pages),
EFI_MEMORY_RP
);
//
// Normally we should ASSERT the returned Status. But there might be memory
// alloc/free involved in SetMemoryAttributes(), which might fail this
// calling. It's rare case so it's OK to let a few tiny holes be not-guarded.
//
if (EFI_ERROR (Status)) {
DEBUG ((DEBUG_WARN, "Failed to guard freed pages: %p (%lu)\n", BaseAddress, (UINT64)Pages));
}
mOnGuarding = FALSE;
}
}
/**
Record freed pages as well as mark them as not-present, if enabled.
@param[in] BaseAddress Base address of just freed pages.
@param[in] Pages Number of freed pages.
@return VOID.
**/
VOID
EFIAPI
GuardFreedPagesChecked (
IN EFI_PHYSICAL_ADDRESS BaseAddress,
IN UINTN Pages
)
{
if (IsHeapGuardEnabled (GUARD_HEAP_TYPE_FREED)) {
GuardFreedPages (BaseAddress, Pages);
}
}
/**
Mark all pages freed before CPU Arch Protocol as not-present.
**/
VOID
GuardAllFreedPages (
VOID
)
{
UINTN Entries[GUARDED_HEAP_MAP_TABLE_DEPTH];
UINTN Shifts[GUARDED_HEAP_MAP_TABLE_DEPTH];
UINTN Indices[GUARDED_HEAP_MAP_TABLE_DEPTH];
UINT64 Tables[GUARDED_HEAP_MAP_TABLE_DEPTH];
UINT64 Addresses[GUARDED_HEAP_MAP_TABLE_DEPTH];
UINT64 TableEntry;
UINT64 Address;
UINT64 GuardPage;
INTN Level;
UINTN BitIndex;
UINTN GuardPageNumber;
if (mGuardedMemoryMap == 0 ||
mMapLevel == 0 ||
mMapLevel > GUARDED_HEAP_MAP_TABLE_DEPTH) {
return;
}
CopyMem (Entries, mLevelMask, sizeof (Entries));
CopyMem (Shifts, mLevelShift, sizeof (Shifts));
SetMem (Tables, sizeof(Tables), 0);
SetMem (Addresses, sizeof(Addresses), 0);
SetMem (Indices, sizeof(Indices), 0);
Level = GUARDED_HEAP_MAP_TABLE_DEPTH - mMapLevel;
Tables[Level] = mGuardedMemoryMap;
Address = 0;
GuardPage = (UINT64)-1;
GuardPageNumber = 0;
while (TRUE) {
if (Indices[Level] > Entries[Level]) {
Tables[Level] = 0;
Level -= 1;
} else {
TableEntry = ((UINT64 *)(UINTN)(Tables[Level]))[Indices[Level]];
Address = Addresses[Level];
if (Level < GUARDED_HEAP_MAP_TABLE_DEPTH - 1) {
Level += 1;
Tables[Level] = TableEntry;
Addresses[Level] = Address;
Indices[Level] = 0;
continue;
} else {
BitIndex = 1;
while (BitIndex != 0) {
if ((TableEntry & BitIndex) != 0) {
if (GuardPage == (UINT64)-1) {
GuardPage = Address;
}
++GuardPageNumber;
} else if (GuardPageNumber > 0) {
GuardFreedPages (GuardPage, GuardPageNumber);
GuardPageNumber = 0;
GuardPage = (UINT64)-1;
}
if (TableEntry == 0) {
break;
}
Address += EFI_PAGES_TO_SIZE (1);
BitIndex = LShiftU64 (BitIndex, 1);
}
}
}
if (Level < (GUARDED_HEAP_MAP_TABLE_DEPTH - (INTN)mMapLevel)) {
break;
}
Indices[Level] += 1;
Address = (Level == 0) ? 0 : Addresses[Level - 1];
Addresses[Level] = Address | LShiftU64 (Indices[Level], Shifts[Level]);
}
//
// Update the maximum address of freed page which can be used for memory
// promotion upon out-of-memory-space.
//
GetLastGuardedFreePageAddress (&Address);
if (Address != 0) {
mLastPromotedPage = Address;
}
}
/**
This function checks to see if the given memory map descriptor in a memory map
can be merged with any guarded free pages.
@param MemoryMapEntry A pointer to a descriptor in MemoryMap.
@param MaxAddress Maximum address to stop the merge.
@return VOID
**/
VOID
MergeGuardPages (
IN EFI_MEMORY_DESCRIPTOR *MemoryMapEntry,
IN EFI_PHYSICAL_ADDRESS MaxAddress
)
{
EFI_PHYSICAL_ADDRESS EndAddress;
UINT64 Bitmap;
INTN Pages;
if (!IsHeapGuardEnabled (GUARD_HEAP_TYPE_FREED) ||
MemoryMapEntry->Type >= EfiMemoryMappedIO) {
return;
}
Bitmap = 0;
Pages = EFI_SIZE_TO_PAGES (MaxAddress - MemoryMapEntry->PhysicalStart);
Pages -= MemoryMapEntry->NumberOfPages;
while (Pages > 0) {
if (Bitmap == 0) {
EndAddress = MemoryMapEntry->PhysicalStart +
EFI_PAGES_TO_SIZE (MemoryMapEntry->NumberOfPages);
Bitmap = GetGuardedMemoryBits (EndAddress, GUARDED_HEAP_MAP_ENTRY_BITS);
}
if ((Bitmap & 1) == 0) {
break;
}
Pages--;
MemoryMapEntry->NumberOfPages++;
Bitmap = RShiftU64 (Bitmap, 1);
}
}
/**
Put part (at most 64 pages a time) guarded free pages back to free page pool.
Freed memory guard is used to detect Use-After-Free (UAF) memory issue, which
makes use of 'Used then throw away' way to detect any illegal access to freed
memory. The thrown-away memory will be marked as not-present so that any access
to those memory (after free) will be caught by page-fault exception.
The problem is that this will consume lots of memory space. Once no memory
left in pool to allocate, we have to restore part of the freed pages to their
normal function. Otherwise the whole system will stop functioning.
@param StartAddress Start address of promoted memory.
@param EndAddress End address of promoted memory.
@return TRUE Succeeded to promote memory.
@return FALSE No free memory found.
**/
BOOLEAN
PromoteGuardedFreePages (
OUT EFI_PHYSICAL_ADDRESS *StartAddress,
OUT EFI_PHYSICAL_ADDRESS *EndAddress
)
{
EFI_STATUS Status;
UINTN AvailablePages;
UINT64 Bitmap;
EFI_PHYSICAL_ADDRESS Start;
if (!IsHeapGuardEnabled (GUARD_HEAP_TYPE_FREED)) {
return FALSE;
}
//
// Similar to memory allocation service, always search the freed pages in
// descending direction.
//
Start = mLastPromotedPage;
AvailablePages = 0;
while (AvailablePages == 0) {
Start -= EFI_PAGES_TO_SIZE (GUARDED_HEAP_MAP_ENTRY_BITS);
//
// If the address wraps around, try the really freed pages at top.
//
if (Start > mLastPromotedPage) {
GetLastGuardedFreePageAddress (&Start);
ASSERT (Start != 0);
Start -= EFI_PAGES_TO_SIZE (GUARDED_HEAP_MAP_ENTRY_BITS);
}
Bitmap = GetGuardedMemoryBits (Start, GUARDED_HEAP_MAP_ENTRY_BITS);
while (Bitmap > 0) {
if ((Bitmap & 1) != 0) {
++AvailablePages;
} else if (AvailablePages == 0) {
Start += EFI_PAGES_TO_SIZE (1);
} else {
break;
}
Bitmap = RShiftU64 (Bitmap, 1);
}
}
if (AvailablePages) {
DEBUG ((DEBUG_INFO, "Promoted pages: %lX (%lx)\r\n", Start, (UINT64)AvailablePages));
ClearGuardedMemoryBits (Start, AvailablePages);
if (gCpu != NULL) {
//
// Set flag to make sure allocating memory without GUARD for page table
// operation; otherwise infinite loops could be caused.
//
mOnGuarding = TRUE;
Status = gCpu->SetMemoryAttributes (gCpu, Start, EFI_PAGES_TO_SIZE(AvailablePages), 0);
ASSERT_EFI_ERROR (Status);
mOnGuarding = FALSE;
}
mLastPromotedPage = Start;
*StartAddress = Start;
*EndAddress = Start + EFI_PAGES_TO_SIZE (AvailablePages) - 1;
return TRUE;
}
return FALSE;
}
/**
Notify function used to set all Guard pages before CPU Arch Protocol installed.
**/
@@ -1212,7 +1592,20 @@ HeapGuardCpuArchProtocolNotify (
)
{
ASSERT (gCpu != NULL);
SetAllGuardPages ();
if (IsHeapGuardEnabled (GUARD_HEAP_TYPE_PAGE|GUARD_HEAP_TYPE_POOL) &&
IsHeapGuardEnabled (GUARD_HEAP_TYPE_FREED)) {
DEBUG ((DEBUG_ERROR, "Heap guard and freed memory guard cannot be enabled at the same time.\n"));
CpuDeadLoop ();
}
if (IsHeapGuardEnabled (GUARD_HEAP_TYPE_PAGE|GUARD_HEAP_TYPE_POOL)) {
SetAllGuardPages ();
}
if (IsHeapGuardEnabled (GUARD_HEAP_TYPE_FREED)) {
GuardAllFreedPages ();
}
}
/**
@@ -1264,6 +1657,10 @@ DumpGuardedMemoryBitmap (
CHAR8 *Ruler1;
CHAR8 *Ruler2;
if (!IsHeapGuardEnabled (GUARD_HEAP_TYPE_ALL)) {
return;
}
if (mGuardedMemoryMap == 0 ||
mMapLevel == 0 ||
mMapLevel > GUARDED_HEAP_MAP_TABLE_DEPTH) {