[PATCH 3.16 299/366] efi: Avoid potential crashes, fix the 'struct efi_pci_io_protocol_32' definition for mixed mode

Ben Hutchings
2018-10-14T23:11:58Z

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

commit 0b3225ab9407f557a8e20f23f37aa7236c10a9b1 upstream.

Mixed mode allows a kernel built for x86_64 to interact with 32-bit
EFI firmware, but requires us to define all struct definitions carefully
when it comes to pointer sizes.

'struct efi_pci_io_protocol_32' currently uses a 'void *' for the
'romimage' field, which will be interpreted as a 64-bit field
on such kernels, potentially resulting in bogus memory references
and subsequent crashes.

Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180504060003.19618-13-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/boot/compressed/eboot.c | 6 ++++--
include/linux/efi.h | 8 ++++----
2 files changed, 8 insertions(+), 6 deletions(-)

--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -358,7 +358,8 @@ __setup_efi_pci32(efi_pci_io_protocol_32
if (status != EFI_SUCCESS)
goto free_struct;

- memcpy(rom->romdata, pci->romimage, pci->romsize);
+ memcpy(rom->romdata, (void *)(unsigned long)pci->romimage,
+ pci->romsize);
return status;

free_struct:
@@ -460,7 +461,8 @@ __setup_efi_pci64(efi_pci_io_protocol_64
if (status != EFI_SUCCESS)
goto free_struct;

- memcpy(rom->romdata, pci->romimage, pci->romsize);
+ memcpy(rom->romdata, (void *)(unsigned long)pci->romimage,
+ pci->romsize);
return status;

free_struct:
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -368,8 +368,8 @@ typedef struct {
u32 attributes;
u32 get_bar_attributes;
u32 set_bar_attributes;
- uint64_t romsize;
- void *romimage;
+ u64 romsize;
+ u32 romimage;
} efi_pci_io_protocol_32;

typedef struct {
@@ -388,8 +388,8 @@ typedef struct {
u64 attributes;
u64 get_bar_attributes;
u64 set_bar_attributes;
- uint64_t romsize;
- void *romimage;
+ u64 romsize;
+ u64 romimage;
} efi_pci_io_protocol_64;

typedef struct {