From 8a6d6299efcffd14c1130942195e6c0d9b50cacd Mon Sep 17 00:00:00 2001 From: Alexey Makhalov Date: Mon, 20 Jul 2020 23:03:05 +0000 Subject: [PATCH] efi: Fix use-after-free in halt/reboot path MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Darren Kenny Reviewed-by: Daniel Kiper Signed-off-by: Stefan Sørensen --- 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/kern/riscv/efi/init.c | 3 +++ grub-core/lib/efi/halt.c | 3 ++- include/grub/loader.h | 1 + 9 files changed, 28 insertions(+), 7 deletions(-) diff --git a/grub-core/kern/arm/efi/init.c b/grub-core/kern/arm/efi/init.c index 06df60e2f..40c3b467f 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 6224999ec..5010caefd 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 c97969a65..9cfd88d77 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 3dfdf2d22..2c31847bf 100644 --- a/grub-core/kern/efi/init.c +++ b/grub-core/kern/efi/init.c @@ -80,5 +80,4 @@ 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 da499aba0..deb2eacd8 100644 --- a/grub-core/kern/i386/efi/init.c +++ b/grub-core/kern/i386/efi/init.c @@ -39,6 +39,11 @@ 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 b5ecbd091..f1965571b 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/kern/riscv/efi/init.c b/grub-core/kern/riscv/efi/init.c index 7eb1969d0..38795fe67 100644 --- a/grub-core/kern/riscv/efi/init.c +++ b/grub-core/kern/riscv/efi/init.c @@ -73,4 +73,7 @@ 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/lib/efi/halt.c b/grub-core/lib/efi/halt.c index 5859f0498..29d413641 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__) && \ !defined(__riscv) grub_acpi_halt (); diff --git a/include/grub/loader.h b/include/grub/loader.h index 7f82a499f..b20864282 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), -- 2.26.2