The root cause is an unnecessary check to Size parameter in function
AdjustMemoryS(). It will cause one standalone free page (happen to have
Guard page around) in the free memory list cannot be allocated, even if
the requested memory size is less than a page.
//
// At least one more page needed for Guard page.
//
if (Size < (SizeRequested + EFI_PAGES_TO_SIZE (1))) {
return 0;
}
The following code in the same function actually covers above check
implicitly. So the fix is simply removing above check.
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Considering following scenario (both NX memory protection and heap guard
are enabled):
1. Allocate 3 pages. The attributes of adjacent memory pages will be
|NOT-PRESENT| present | present | present |NOT-PRESENT|
2. Free the middle page. The attributes of adjacent memory pages should be
|NOT-PRESENT| present |NOT-PRESENT| present |NOT-PRESENT|
But the NX feature will overwrite the attributes of middle page. So it
looks still like below, which is wrong.
|NOT-PRESENT| present | PRESENT | present |NOT-PRESENT|
The solution is checking the first and/or last page of a memory block to be
marked as NX, and skipping them if they are Guard pages.
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
This issue is a regression one caused by a patch at
425d25699b
That fix didn't take the 0 page to free into account, which still
needs to call UnsetGuardPage() even no memory needs to free.
The fix is just moving the calling of UnsetGuardPage() to the place
right after calling AdjustMemoryF().
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
This hole will cause page fault randomly. The root cause is that Guard
page, which is just freed back to page pool but not yet cleared not-
present attribute, will be allocated right away by internal function
CoreFreeMemoryMapStack(). The solution to this issue is to clear the
not-present attribute for freed Guard page before doing any free
operation, instead of after those operation.
The reason we didn't do this before is due to the fact that manipulating
page attributes might cause memory allocation action which would cause a
dead lock inside a memory allocation/free operation. So we always set or
unset Guard page outside the memory lock. After a thorough analysis, we
believe clearing a Guard page will not cause memory allocation because
memory we're to manipulate was already manipulated before for sure.
Therefore there should be no memory allocation occurring in this
situation.
Since we cleared Guard page not-present attribute before freeing instead
of after freeing, the debug code to clear freed memory can now be restored
to its original way (aka no checking and bypassing Guard page).
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Star Zeng <star.zeng@intel.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>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Three issues addressed here:
a. Make NX memory protection and heap guard to be compatible
The solution is to check PcdDxeNxMemoryProtectionPolicy in Heap Guard to
see if the free memory should be set to NX, and set the Guard page to NX
before it's freed back to memory pool. This can solve the issue which NX
setting would be overwritten by Heap Guard feature in certain
configuration.
b. Returned pool address was not 8-byte aligned sometimes
This happened only when BIT7 is not set in PcdHeapGuardPropertyMask. Since
8-byte alignment is UEFI spec required, letting allocated pool adjacent to
tail guard page cannot be guaranteed.
c. NULL address handling due to allocation failure
When allocation failure, normally a NULL will be returned. But Heap Guard
code will still try to adjust the starting address of it, which will cause
a non-NULL pointer returned.
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
One issue is that macros defined in HeapGuard.h
GUARD_HEAP_TYPE_PAGE
GUARD_HEAP_TYPE_POOL
doesn't match the definition of PCD PcdHeapGuardPropertyMask in
MdeModulePkg.dec. This patch fixed it by exchanging the BIT0 and BIT1
of them.
Another is that method AdjustMemoryF() will return a bigger NumberOfPages than
the value passed in. This is caused by counting twice of a shared Guard page
which can be used for both head and tail Guard of the memory before it and
after it. This happens only when partially freeing just one page in the middle
of a bunch of allocated pages. The freed page should be turned into a new
Guard page.
Cc: Jie Lin <jie.lin@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.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>
In the method DumpGuardedMemoryBitmap() and SetAllGuardPages(), the code
didn't check if the global mMapLevel is legal value or not, which leaves
a logic hole causing potential array overflow in code followed.
This patch adds sanity check before any array reference in those methods.
Cc: Wu Hao <hao.a.wu@intel.com>
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Wu Hao <hao.a.wu@intel.com>
The build error is introduced by following check in:
2930ef9809235a4490c8
The Visual Studio older than 2015 doesn't support constant integer
in binary format (0bxxx). This patch changes them to BIT macro to
fix it. This patch also cleans up coding style about unmatched
comment for return value.
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Bi Dandan <dandan.bi@intel.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 feature makes use of paging mechanism to add a hidden (not present)
page just before and after the allocated memory block. If the code tries
to access memory outside of the allocated part, page fault exception will
be triggered.
This feature is controlled by three PCDs:
gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask
gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPoolType
gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPageType
BIT0 and BIT1 of PcdHeapGuardPropertyMask can be used to enable or disable
memory guard for page and pool respectively. PcdHeapGuardPoolType and/or
PcdHeapGuardPageType are used to enable or disable guard for specific type
of memory. For example, we can turn on guard only for EfiBootServicesData
and EfiRuntimeServicesData by setting the PCD with value 0x50.
Pool memory is not ususally integer multiple of one page, and is more likely
less than a page. There's no way to monitor the overflow at both top and
bottom of pool memory. BIT7 of PcdHeapGuardPropertyMask is used to control
how to position the head of pool memory so that it's easier to catch memory
overflow in memory growing direction or in decreasing direction.
Note1: Turning on heap guard, especially pool guard, will introduce too many
memory fragments. Windows 10 has a limitation in its boot loader, which
accepts at most 512 memory descriptors passed from BIOS. This will prevent
Windows 10 from booting if heap guard is enabled. The latest Linux
distribution with grub boot loader has no such issue. Normally it's not
recommended to enable this feature in production build of BIOS.
Note2: Don't enable this feature for NT32 emulation platform which doesn't
support paging.
Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Suggested-by: Ayellet Wolman <ayellet.wolman@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
Jian J Wang