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 4.19.3: adjust context in update_fdt()]
[dannf: Moved init_lockdown() call after uefi_init(), fixing SB detection]

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 1a6a77df8a5e8aea45f3cbc2bac9c5d0883b0edb..04d9e8fa9a0f7cf1b378be09579a3d671526e0a8 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>
 
@@ -257,6 +258,9 @@ void __init efi_init(void)
                return;
        }
 
+       efi_set_secure_boot(params.secure_boot);
+       init_lockdown();
+
        reserve_regions();
        efi_esrt_init();
 

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 2a29dd9c986d4e2df7663aa1305df8adbaa59739..7bebfa7ab83188b6650477c7fefa39a424e15d78 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -657,7 +657,8 @@ 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 dba296a44f4ec27dda6f73a00d716837c9aa106c..7da77b31f8c1acb50858943dde1718192d092a14 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 a2f5498775f2abca11f97f06ff4f7e5c9195820d..11cdbdd9c475b81e652c02c0baace3c82bda3239 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 {