> v2 changes: > a. Drop PCD PcdUseAfterFreeDetectionPropertyMask. Use BIT4 of > PcdHeapGuardPropertyMask instead. Update related descriptions in both > dec and uni files.
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 heap 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, this patch series add logic 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 freed. BIT4 of following PCD is used to enable the freed-memory guard feature. gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPropertyMask Please note this feature cannot be enabled with heap guard at the same time. Cc: Star Zeng <[email protected]> Cc: Michael D Kinney <[email protected]> Cc: Jiewen Yao <[email protected]> Cc: Ruiyu Ni <[email protected]> Cc: Laszlo Ersek <[email protected]> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Jian J Wang <[email protected]> --- MdeModulePkg/MdeModulePkg.dec | 10 ++++++++++ MdeModulePkg/MdeModulePkg.uni | 6 +++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec index 6037504fa7..255b92ea67 100644 --- a/MdeModulePkg/MdeModulePkg.dec +++ b/MdeModulePkg/MdeModulePkg.dec @@ -955,6 +955,8 @@ # free pages for all of them. The page allocation for the type related to # cleared bits keeps the same as ususal. # + # This PCD is only valid if BIT0 and/or BIT2 are set in PcdHeapGuardPropertyMask. + # # Below is bit mask for this PCD: (Order is same as UEFI spec)<BR> # EfiReservedMemoryType 0x0000000000000001<BR> # EfiLoaderCode 0x0000000000000002<BR> @@ -984,6 +986,8 @@ # if there's enough free memory for all of them. The pool allocation for the # type related to cleared bits keeps the same as ususal. # + # This PCD is only valid if BIT1 and/or BIT3 are set in PcdHeapGuardPropertyMask. + # # Below is bit mask for this PCD: (Order is same as UEFI spec)<BR> # EfiReservedMemoryType 0x0000000000000001<BR> # EfiLoaderCode 0x0000000000000002<BR> @@ -1007,14 +1011,20 @@ gEfiMdeModulePkgTokenSpaceGuid.PcdHeapGuardPoolType|0x0|UINT64|0x30001053 ## This mask is to control Heap Guard behavior. + # # Note that due to the limit of pool memory implementation and the alignment # requirement of UEFI spec, BIT7 is a try-best setting which cannot guarantee # that the returned pool is exactly adjacent to head guard page or tail guard # page. + # + # Note that UEFI freed-memory guard and pool/page guard cannot be enabled + # at the same time. + # # BIT0 - Enable UEFI page guard.<BR> # BIT1 - Enable UEFI pool guard.<BR> # BIT2 - Enable SMM page guard.<BR> # BIT3 - Enable SMM pool guard.<BR> + # BIT4 - Enable UEFI freed-memory guard (Use-After-Free memory detection).<BR> # BIT6 - Enable non-stop mode.<BR> # BIT7 - The direction of Guard Page for Pool Guard. # 0 - The returned pool is near the tail guard page.<BR> diff --git a/MdeModulePkg/MdeModulePkg.uni b/MdeModulePkg/MdeModulePkg.uni index a6bcb627cf..e72b893509 100644 --- a/MdeModulePkg/MdeModulePkg.uni +++ b/MdeModulePkg/MdeModulePkg.uni @@ -1171,6 +1171,7 @@ " before and after corresponding type of pages allocated if there's enough\n" " free pages for all of them. The page allocation for the type related to\n" " cleared bits keeps the same as ususal.\n\n" + " This PCD is only valid if BIT0 and/or BIT2 are set in PcdHeapGuardPropertyMask.\n\n" " Below is bit mask for this PCD: (Order is same as UEFI spec)<BR>\n" " EfiReservedMemoryType 0x0000000000000001\n" " EfiLoaderCode 0x0000000000000002\n" @@ -1198,6 +1199,7 @@ " before and after corresponding type of pages which the allocated pool occupies,\n" " if there's enough free memory for all of them. The pool allocation for the\n" " type related to cleared bits keeps the same as ususal.\n\n" + " This PCD is only valid if BIT1 and/or BIT3 are set in PcdHeapGuardPropertyMask.\n\n" " Below is bit mask for this PCD: (Order is same as UEFI spec)<BR>\n" " EfiReservedMemoryType 0x0000000000000001\n" " EfiLoaderCode 0x0000000000000002\n" @@ -1225,11 +1227,13 @@ "Note that due to the limit of pool memory implementation and the alignment\n" "requirement of UEFI spec, BIT7 is a try-best setting which cannot guarantee\n" "that the returned pool is exactly adjacent to head guard page or tail guard\n" - "page.\n" + "page.\n\n" + "Note that UEFI freed-memory guard and pool/page guard cannot be enabled at the same time.\n\n" " BIT0 - Enable UEFI page guard.<BR>\n" " BIT1 - Enable UEFI pool guard.<BR>\n" " BIT2 - Enable SMM page guard.<BR>\n" " BIT3 - Enable SMM pool guard.<BR>\n" + " BIT4 - Enable UEFI freed-memory guard (Use-After-Free memory detection).<BR>\n" " BIT7 - The direction of Guard Page for Pool Guard.\n" " 0 - The returned pool is near the tail guard page.<BR>\n" " 1 - The returned pool is near the head guard page.<BR>" -- 2.16.2.windows.1 _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
