From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Alexey Makhalov <amakhalov@vmware.com>

Date: Mon, 20 Jul 2020 23:03:05 +0000

Subject: [PATCH] efi: Fix use-after-free in halt/reboot path

commit 92bfc33db984 ("efi: Free malloc regions on exit")

introduced memory freeing in grub_efi_fini(), which is

used not only by exit path but by halt/reboot one as well.

As result of memory freeing, code and data regions used by

modules, such as halt, reboot, acpi (used by halt) also got

freed. After return to module code, CPU executes, filled

by UEFI firmware (tested with edk2), 0xAFAFAFAF pattern as

a code. Which leads to #UD exception later.

grub> halt

!!!! X64 Exception Type - 06(#UD - Invalid Opcode)  CPU Apic ID - 00000000 !!!!

RIP  - 0000000003F4EC28, CS  - 0000000000000038, RFLAGS - 0000000000200246

RAX  - 0000000000000000, RCX - 00000000061DA188, RDX - 0A74C0854DC35D41

RBX  - 0000000003E10E08, RSP - 0000000007F0F860, RBP - 0000000000000000

RSI  - 00000000064DB768, RDI - 000000000832C5C3

R8   - 0000000000000002, R9  - 0000000000000000, R10 - 00000000061E2E52

R11  - 0000000000000020, R12 - 0000000003EE5C1F, R13 - 00000000061E0FF4

R14  - 0000000003E10D80, R15 - 00000000061E2F60

DS   - 0000000000000030, ES  - 0000000000000030, FS  - 0000000000000030

GS   - 0000000000000030, SS  - 0000000000000030

CR0  - 0000000080010033, CR2 - 0000000000000000, CR3 - 0000000007C01000

CR4  - 0000000000000668, CR8 - 0000000000000000

DR0  - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000

DR3  - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400

GDTR - 00000000079EEA98 0000000000000047, LDTR - 0000000000000000

IDTR - 0000000007598018 0000000000000FFF,   TR - 0000000000000000

FXSAVE_STATE - 0000000007F0F4C0

Proposal here is to continue to free allocated memory for

exit boot services path but keep it for halt/reboot path

as it won't be much security concern here.

Introduced GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY

loader flag to be used by efi halt/reboot path.

Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>

Reviewed-by: Darren Kenny <darren.kenny@oracle.com>

---

 grub-core/kern/arm/efi/init.c   | 3 +++

 grub-core/kern/arm64/efi/init.c | 3 +++

 grub-core/kern/efi/efi.c        | 3 ++-

 grub-core/kern/efi/init.c       | 1 -

 grub-core/kern/i386/efi/init.c  | 9 +++++++--

 grub-core/kern/ia64/efi/init.c  | 9 +++++++--

 grub-core/lib/efi/halt.c        | 3 ++-

 include/grub/loader.h           | 1 +

 8 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/grub-core/kern/arm/efi/init.c b/grub-core/kern/arm/efi/init.c

index 06df60e2f0e..40c3b467fc6 100644

--- a/grub-core/kern/arm/efi/init.c

+++ b/grub-core/kern/arm/efi/init.c

@@ -71,4 +71,7 @@ grub_machine_fini (int flags)

   efi_call_1 (b->close_event, tmr_evt);

   grub_efi_fini ();

+

+  if (!(flags & GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY))

+    grub_efi_memory_fini ();

 }

diff --git a/grub-core/kern/arm64/efi/init.c b/grub-core/kern/arm64/efi/init.c

index 6224999ec9c..5010caefd66 100644

--- a/grub-core/kern/arm64/efi/init.c

+++ b/grub-core/kern/arm64/efi/init.c

@@ -57,4 +57,7 @@ grub_machine_fini (int flags)

     return;

   grub_efi_fini ();

+

+  if (!(flags & GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY))

+    grub_efi_memory_fini ();

 }

diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c

index 03de9cb14e7..5dfcf943322 100644

--- a/grub-core/kern/efi/efi.c

+++ b/grub-core/kern/efi/efi.c

@@ -157,7 +157,8 @@ grub_efi_get_loaded_image (grub_efi_handle_t image_handle)

 void

 grub_reboot (void)

 {

-  grub_machine_fini (GRUB_LOADER_FLAG_NORETURN);

+  grub_machine_fini (GRUB_LOADER_FLAG_NORETURN |

+		     GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY);

   efi_call_4 (grub_efi_system_table->runtime_services->reset_system,

               GRUB_EFI_RESET_COLD, GRUB_EFI_SUCCESS, 0, NULL);

   for (;;) ;

diff --git a/grub-core/kern/efi/init.c b/grub-core/kern/efi/init.c

index e6183a4c44d..79243b364a1 100644

--- a/grub-core/kern/efi/init.c

+++ b/grub-core/kern/efi/init.c

@@ -136,5 +136,4 @@ grub_efi_fini (void)

 {

   grub_efidisk_fini ();

   grub_console_fini ();

-  grub_efi_memory_fini ();

 }

diff --git a/grub-core/kern/i386/efi/init.c b/grub-core/kern/i386/efi/init.c

index a28316cc640..46476e27eae 100644

--- a/grub-core/kern/i386/efi/init.c

+++ b/grub-core/kern/i386/efi/init.c

@@ -38,6 +38,11 @@ grub_machine_init (void)

 void

 grub_machine_fini (int flags)

 {

-  if (flags & GRUB_LOADER_FLAG_NORETURN)

-    grub_efi_fini ();

+  if (!(flags & GRUB_LOADER_FLAG_NORETURN))

+    return;

+

+  grub_efi_fini ();

+

+  if (!(flags & GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY))

+    grub_efi_memory_fini ();

 }

diff --git a/grub-core/kern/ia64/efi/init.c b/grub-core/kern/ia64/efi/init.c

index b5ecbd09121..f1965571b1d 100644

--- a/grub-core/kern/ia64/efi/init.c

+++ b/grub-core/kern/ia64/efi/init.c

@@ -70,6 +70,11 @@ grub_machine_init (void)

 void

 grub_machine_fini (int flags)

 {

-  if (flags & GRUB_LOADER_FLAG_NORETURN)

-    grub_efi_fini ();

+  if (!(flags & GRUB_LOADER_FLAG_NORETURN))

+    return;

+

+  grub_efi_fini ();

+

+  if (!(flags & GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY))

+    grub_efi_memory_fini ();

 }

diff --git a/grub-core/lib/efi/halt.c b/grub-core/lib/efi/halt.c

index e9441c844ac..a69a77681e3 100644

--- a/grub-core/lib/efi/halt.c

+++ b/grub-core/lib/efi/halt.c

@@ -28,7 +28,8 @@

 void

 grub_halt (void)

 {

-  grub_machine_fini (GRUB_LOADER_FLAG_NORETURN);

+  grub_machine_fini (GRUB_LOADER_FLAG_NORETURN |

+		     GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY);

 #if !defined(__ia64__) && !defined(__arm__) && !defined(__aarch64__)

   grub_acpi_halt ();

 #endif

diff --git a/include/grub/loader.h b/include/grub/loader.h

index 7f82a499fd9..b208642821b 100644

--- a/include/grub/loader.h

+++ b/include/grub/loader.h

@@ -33,6 +33,7 @@ enum

 {

   GRUB_LOADER_FLAG_NORETURN = 1,

   GRUB_LOADER_FLAG_PXE_NOT_UNLOAD = 2,

+  GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY = 4,

 };

 void EXPORT_FUNC (grub_loader_set) (grub_err_t (*boot) (void),