Randstruct by default randomizes structures that consist entirely of
function pointers, even if they are not explicitly labeled for
randomization. efi_rng_protocol contains an anonymous structure that is
affected by this implicit selection process. Randomization of this
structure causes a data layout inconsistency between the kernel and the
EFI. In this scenario the Arm64 boot process fails with the following
output:
EFI stub: Booting Linux Kernel...
EFI stub: ERROR: efi_get_random_bytes() failed (0x8000000000000002)
EFI stub: Using DTB from configuration table
EFI stub: Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID device path
Synchronous Exception at 0x0000000081310C90
Synchronous Exception at 0x0000000081310C90
efi_get_random_bytes() fails in handle_kernel_image (arm64-stub.c)
because it uses an incorrect structure layout for efi_call_proto. Add
the __no_randomize_layout annotation to the anonymous structure within
efi_rng_protocol to prevent its randomization and resolve this issue.
This patch was tested for the Arm64 architecture using QEMU. In
addition to the current next branch of this subsystem, also minor
versions 4.16 to 5.1, 5.5 and 5.6 were tested successfully with a
(backported) version of this patch.
Signed-off-by: Daniel Marth <daniel.marth@xxxxxxxxxxxxxxxxx>
---
drivers/firmware/efi/libstub/random.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c
index 24aa37535372..54fa980cf1af 100644
--- a/drivers/firmware/efi/libstub/random.c
+++ b/drivers/firmware/efi/libstub/random.c
@@ -18,7 +18,7 @@ union efi_rng_protocol {
efi_status_t (__efiapi *get_rng)(efi_rng_protocol_t *,
efi_guid_t *, unsigned long,
u8 *out);
- };
+ } __no_randomize_layout;
struct {
u32 get_info;
u32 get_rng;
--
2.37.2
