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From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Alexey Makhalov <amakhalov@vmware.com>
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Date: Mon, 20 Jul 2020 23:03:05 +0000
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Subject: [PATCH] efi: Fix use-after-free in halt/reboot path
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commit 92bfc33db984 ("efi: Free malloc regions on exit")
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introduced memory freeing in grub_efi_fini(), which is
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used not only by exit path but by halt/reboot one as well.
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As result of memory freeing, code and data regions used by
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modules, such as halt, reboot, acpi (used by halt) also got
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freed. After return to module code, CPU executes, filled
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by UEFI firmware (tested with edk2), 0xAFAFAFAF pattern as
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a code. Which leads to #UD exception later.
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grub> halt
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!!!! X64 Exception Type - 06(#UD - Invalid Opcode) CPU Apic ID - 00000000 !!!!
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RIP - 0000000003F4EC28, CS - 0000000000000038, RFLAGS - 0000000000200246
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RAX - 0000000000000000, RCX - 00000000061DA188, RDX - 0A74C0854DC35D41
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RBX - 0000000003E10E08, RSP - 0000000007F0F860, RBP - 0000000000000000
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RSI - 00000000064DB768, RDI - 000000000832C5C3
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R8 - 0000000000000002, R9 - 0000000000000000, R10 - 00000000061E2E52
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R11 - 0000000000000020, R12 - 0000000003EE5C1F, R13 - 00000000061E0FF4
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R14 - 0000000003E10D80, R15 - 00000000061E2F60
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DS - 0000000000000030, ES - 0000000000000030, FS - 0000000000000030
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GS - 0000000000000030, SS - 0000000000000030
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CR0 - 0000000080010033, CR2 - 0000000000000000, CR3 - 0000000007C01000
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CR4 - 0000000000000668, CR8 - 0000000000000000
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DR0 - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
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DR3 - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
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GDTR - 00000000079EEA98 0000000000000047, LDTR - 0000000000000000
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IDTR - 0000000007598018 0000000000000FFF, TR - 0000000000000000
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FXSAVE_STATE - 0000000007F0F4C0
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Proposal here is to continue to free allocated memory for
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exit boot services path but keep it for halt/reboot path
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as it won't be much security concern here.
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Introduced GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY
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loader flag to be used by efi halt/reboot path.
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Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
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Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
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---
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grub-core/kern/arm/efi/init.c | 3 +++
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grub-core/kern/efi/efi.c | 7 ++++---
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grub-core/kern/i386/efi/init.c | 9 +++++++--
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grub-core/kern/ia64/efi/init.c | 9 +++++++--
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grub-core/lib/efi/halt.c | 3 ++-
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include/grub/loader.h | 1 +
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6 files changed, 24 insertions(+), 8 deletions(-)
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diff --git a/grub-core/kern/arm/efi/init.c b/grub-core/kern/arm/efi/init.c
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index 06df60e2f0e..40c3b467fc6 100644
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--- a/grub-core/kern/arm/efi/init.c
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+++ b/grub-core/kern/arm/efi/init.c
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@@ -71,4 +71,7 @@ grub_machine_fini (int flags)
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efi_call_1 (b->close_event, tmr_evt);
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grub_efi_fini ();
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+
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+ if (!(flags & GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY))
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+ grub_efi_memory_fini ();
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}
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diff --git a/grub-core/kern/efi/efi.c b/grub-core/kern/efi/efi.c
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index 42c68307f3f..6c4099a685d 100644
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--- a/grub-core/kern/efi/efi.c
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+++ b/grub-core/kern/efi/efi.c
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@@ -162,9 +162,10 @@ grub_exit (int retval)
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if (retval == 0)
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rc = GRUB_EFI_SUCCESS;
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- grub_machine_fini (GRUB_LOADER_FLAG_NORETURN);
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- efi_call_4 (grub_efi_system_table->boot_services->exit,
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- grub_efi_image_handle, rc, 0, 0);
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+ grub_machine_fini (GRUB_LOADER_FLAG_NORETURN |
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+ GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY);
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+ efi_call_4 (grub_efi_system_table->runtime_services->reset_system,
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+ GRUB_EFI_RESET_COLD, rc, 0, NULL);
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for (;;) ;
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}
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diff --git a/grub-core/kern/i386/efi/init.c b/grub-core/kern/i386/efi/init.c
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index a28316cc640..46476e27eae 100644
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--- a/grub-core/kern/i386/efi/init.c
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+++ b/grub-core/kern/i386/efi/init.c
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@@ -38,6 +38,11 @@ grub_machine_init (void)
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void
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grub_machine_fini (int flags)
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{
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- if (flags & GRUB_LOADER_FLAG_NORETURN)
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- grub_efi_fini ();
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+ if (!(flags & GRUB_LOADER_FLAG_NORETURN))
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+ return;
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+
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+ grub_efi_fini ();
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+
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+ if (!(flags & GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY))
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+ grub_efi_memory_fini ();
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}
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diff --git a/grub-core/kern/ia64/efi/init.c b/grub-core/kern/ia64/efi/init.c
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index b5ecbd09121..f1965571b1d 100644
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--- a/grub-core/kern/ia64/efi/init.c
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+++ b/grub-core/kern/ia64/efi/init.c
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@@ -70,6 +70,11 @@ grub_machine_init (void)
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void
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grub_machine_fini (int flags)
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{
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- if (flags & GRUB_LOADER_FLAG_NORETURN)
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- grub_efi_fini ();
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+ if (!(flags & GRUB_LOADER_FLAG_NORETURN))
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+ return;
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+
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+ grub_efi_fini ();
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+
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+ if (!(flags & GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY))
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+ grub_efi_memory_fini ();
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}
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diff --git a/grub-core/lib/efi/halt.c b/grub-core/lib/efi/halt.c
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index e9441c844ac..a69a77681e3 100644
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--- a/grub-core/lib/efi/halt.c
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+++ b/grub-core/lib/efi/halt.c
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@@ -28,7 +28,8 @@
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void
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grub_halt (void)
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{
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- grub_machine_fini (GRUB_LOADER_FLAG_NORETURN);
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+ grub_machine_fini (GRUB_LOADER_FLAG_NORETURN |
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+ GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY);
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#if !defined(__ia64__) && !defined(__arm__) && !defined(__aarch64__)
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grub_acpi_halt ();
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#endif
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diff --git a/include/grub/loader.h b/include/grub/loader.h
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index 7f82a499fd9..b208642821b 100644
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--- a/include/grub/loader.h
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+++ b/include/grub/loader.h
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@@ -33,6 +33,7 @@ enum
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{
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GRUB_LOADER_FLAG_NORETURN = 1,
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GRUB_LOADER_FLAG_PXE_NOT_UNLOAD = 2,
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+ GRUB_LOADER_FLAG_EFI_KEEP_ALLOCATED_MEMORY = 4,
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};
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void EXPORT_FUNC (grub_loader_set) (grub_err_t (*boot) (void),
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