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

Bug-Debian: https://bugs.debian.org/831827
Forwarded: no

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]
[bwh: Drop call to init_lockdown(), as efi_set_secure_boot() now calls this]
[bwh: Forward-ported to 5.6: efi_get_secureboot() no longer takes a
 sys_table parameter]
[bwh: Forward-ported to 5.7: EFI initialisation from FDT was rewritten, so:
 - Add Secure Boot mode to the parameter enumeration in fdtparams.c
 - Add a parameter to efi_get_fdt_params() to return the Secure Boot mode
 - Since Xen does not have a property name defined for Secure Boot mode,
   change efi_get_fdt_prop() to handle a missing property name by clearing
   the output variable]
[Salvatore Bonaccorso: Forward-ported to 5.10: f30f242fb131 ("efi: Rename
arm-init to efi-init common for all arch") renamed arm-init.c to efi-init.c]

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/efi-init.c b/drivers/firmware/efi/efi-init.c
index b2c829e95bd14ba830aa67fa5b87e82f0a4b81e8..a087f4e7d140128e2b24988348a4b759979e230d 100644 (file)
--- a/drivers/firmware/efi/efi-init.c
+++ b/drivers/firmware/efi/efi-init.c
@@ -210,9 +210,10 @@ void __init efi_init(void)
 {
        struct efi_memory_map_data data;
        u64 efi_system_table;
+       u32 secure_boot;
 
        /* Grab UEFI information placed in FDT by stub */
-       efi_system_table = efi_get_fdt_params(&data);
+       efi_system_table = efi_get_fdt_params(&data, &secure_boot);
        if (!efi_system_table)
                return;
 
@@ -234,6 +235,8 @@ void __init efi_init(void)
                return;
        }
 
+       efi_set_secure_boot(secure_boot);
+
        reserve_regions();
        /*
         * For memblock manipulation, the cap should come after the memblock_add().

diff --git a/drivers/firmware/efi/fdtparams.c b/drivers/firmware/efi/fdtparams.c
index e901f8564ca0c5741b3755f8333812fdbd69591e..12b8f0b485906ccacc9c8bdfee15a5224b045ce3 100644 (file)
--- a/drivers/firmware/efi/fdtparams.c
+++ b/drivers/firmware/efi/fdtparams.c
@@ -16,6 +16,7 @@ enum {
        MMSIZE,
        DCSIZE,
        DCVERS,
+       SBMODE,
 
        PARAMCOUNT
 };
@@ -26,6 +27,7 @@ static __initconst const char name[][22] = {
        [MMSIZE] = "MemMap Size          ",
        [DCSIZE] = "MemMap Desc. Size    ",
        [DCVERS] = "MemMap Desc. Version ",
+       [SBMODE] = "Secure Boot Enabled  ",
 };
 
 static __initconst const struct {
@@ -41,6 +43,7 @@ static __initconst const struct {
                        [MMSIZE] = "xen,uefi-mmap-size",
                        [DCSIZE] = "xen,uefi-mmap-desc-size",
                        [DCVERS] = "xen,uefi-mmap-desc-ver",
+                       [SBMODE] = "",
                }
        }, {
 #endif
@@ -51,6 +54,7 @@ static __initconst const struct {
                        [MMSIZE] = "linux,uefi-mmap-size",
                        [DCSIZE] = "linux,uefi-mmap-desc-size",
                        [DCVERS] = "linux,uefi-mmap-desc-ver",
+                       [SBMODE] = "linux,uefi-secure-boot",
                }
        }
 };
@@ -62,6 +66,11 @@ static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
        int len;
        u64 val;
 
+       if (!pname[0]) {
+               memset(var, 0, size);
+               return 0;
+       }
+
        prop = fdt_getprop(fdt, node, pname, &len);
        if (!prop)
                return 1;
@@ -79,7 +88,7 @@ static int __init efi_get_fdt_prop(const void *fdt, int node, const char *pname,
        return 0;
 }
 
-u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
+u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm, u32 *secure_boot)
 {
        const void *fdt = initial_boot_params;
        unsigned long systab;
@@ -93,6 +102,7 @@ u64 __init efi_get_fdt_params(struct efi_memory_map_data *mm)
                [MMSIZE] = { &mm->size,         sizeof(mm->size) },
                [DCSIZE] = { &mm->desc_size,    sizeof(mm->desc_size) },
                [DCVERS] = { &mm->desc_version, sizeof(mm->desc_version) },
+               [SBMODE] = { secure_boot,       sizeof(*secure_boot) },
        };
 
        BUILD_BUG_ON(ARRAY_SIZE(target) != ARRAY_SIZE(name));

diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index fe567be0f118beb18ec061850e17b3c8ae77945a..25def8a20faa1fbc7c4f3cd93fb5820d31f11271 100644 (file)
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -148,6 +148,12 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
                }
        }
 
+       fdt_val32 = cpu_to_fdt32(efi_get_secureboot());
+       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 2d643ad0d636e03cb7723f86148f38e21cd2102e..d4590682f775d795b0504a504326d67c925b2251 100644 (file)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -710,7 +710,8 @@ extern void efi_mem_reserve(phys_addr_t addr, u64 size);
 extern int efi_mem_reserve_persistent(phys_addr_t addr, u64 size);
 extern void efi_initialize_iomem_resources(struct resource *code_resource,
                struct resource *data_resource, struct resource *bss_resource);
-extern u64 efi_get_fdt_params(struct efi_memory_map_data *data);
+extern u64 efi_get_fdt_params(struct efi_memory_map_data *data,
+                             u32 *secure_boot);
 extern struct kobject *efi_kobj;
 
 extern int efi_reboot_quirk_mode;