arm64: add kernel config option to lock down when in Secure Boot mode

Add a kernel configuration option to lock down the kernel, to restrict
userspace's ability to modify the running kernel when UEFI Secure Boot is
enabled. Based on the x86 patch by Matthew Garrett.

Determine the state of Secure Boot in the EFI stub and pass this to the
kernel using the FDT.

Signed-off-by: Linn Crosetto <linn@hpe.com>
[bwh: Forward-ported to 4.10: adjust context]
[Lukas Wunner: Forward-ported to 4.11: drop parts applied upstream]
[bwh: Forward-ported to 4.15 and lockdown patch set:
 - Pass result of efi_get_secureboot() in stub through to
   efi_set_secure_boot() in main kernel
 - Use lockdown API and naming]
[bwh: Forward-ported to 4.18.20: adjust context in update_fdt()]

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name arm64-add-kernel-config-option-to-lock-down-when.patch

diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
index 388a929baf95d1e1107ab4b0ab20516dea3cfdf7..930997ddcf195dccb7cf6c6eba5b3ac4109705f1 100644 (file)
--- a/drivers/firmware/efi/arm-init.c
+++ b/drivers/firmware/efi/arm-init.c
@@ -21,6 +21,7 @@
 #include <linux/of_fdt.h>
 #include <linux/platform_device.h>
 #include <linux/screen_info.h>
+#include <linux/security.h>
 
 #include <asm/efi.h>
 
@@ -252,6 +253,9 @@ void __init efi_init(void)
             "Unexpected EFI_MEMORY_DESCRIPTOR version %ld",
              efi.memmap.desc_version);
 
+       efi_set_secure_boot(params.secure_boot);
+       init_lockdown();
+
        if (uefi_init() < 0) {
                efi_memmap_unmap();
                return;

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 232f4915223b519b3ee6580cb08354ac9b0a7016..89f26b721c8f85bd91ab1057d7b54f2f99dbf8e6 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -648,7 +648,8 @@ static __initdata struct params fdt_params[] = {
        UEFI_PARAM("MemMap Address", "linux,uefi-mmap-start", mmap),
        UEFI_PARAM("MemMap Size", "linux,uefi-mmap-size", mmap_size),
        UEFI_PARAM("MemMap Desc. Size", "linux,uefi-mmap-desc-size", desc_size),
-       UEFI_PARAM("MemMap Desc. Version", "linux,uefi-mmap-desc-ver", desc_ver)
+       UEFI_PARAM("MemMap Desc. Version", "linux,uefi-mmap-desc-ver", desc_ver),
+       UEFI_PARAM("Secure Boot Enabled", "linux,uefi-secure-boot", secure_boot)
 };
 
 static __initdata struct params xen_fdt_params[] = {

diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index 0c0d2312f4a8ad27f6e852bc82d5f2b6c0124e64..3dae6e668c2f3b7d950422c8c2e33fe7bc7539d7 100644 (file)
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -159,6 +159,12 @@ static efi_status_t update_fdt(efi_system_table_t *sys_table, void *orig_fdt,
                }
        }
 
+       fdt_val32 = cpu_to_fdt32(efi_get_secureboot(sys_table));
+       status = fdt_setprop(fdt, node, "linux,uefi-secure-boot",
+                            &fdt_val32, sizeof(fdt_val32));
+       if (status)
+               goto fdt_set_fail;
+
        /* shrink the FDT back to its minimum size */
        fdt_pack(fdt);
 

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 642151176844401069c54a8fe6d782be6e70b6c5..d969c10a093ad4b8582a8a39689b8fc555f50dd0 100644 (file)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -786,6 +786,7 @@ struct efi_fdt_params {
        u32 mmap_size;
        u32 desc_size;
        u32 desc_ver;
+       u32 secure_boot;
 };
 
 typedef struct {