efi/arm64: libstub: Deal gracefully with EFI_RNG_PROTOCOL failure

Currently, on arm64, we abort on any failure from efi_get_random_bytes()
other than EFI_NOT_FOUND when it comes to setting the physical seed for
KASLR, but ignore such failures when obtaining the seed for virtual
KASLR or for early seeding of the kernel's entropy pool via the config
table. This is inconsistent, and may lead to unexpected boot failures.

So let's permit any failure for the physical seed, and simply report
the error code if it does not equal EFI_NOT_FOUND.

Cc: <stable@vger.kernel.org> # v5.8+
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index e5bfac79e5ac972a283f3867b0f0325a22e5e846..04f5d79d4265373b9c7acc375d00dbf24266950f 100644 (file)
--- a/drivers/firmware/efi/libstub/arm64-stub.c
+++ b/drivers/firmware/efi/libstub/arm64-stub.c
@@ -62,10 +62,12 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
                        status = efi_get_random_bytes(sizeof(phys_seed),
                                                      (u8 *)&phys_seed);
                        if (status == EFI_NOT_FOUND) {
-                               efi_info("EFI_RNG_PROTOCOL unavailable, no randomness supplied\n");
+                               efi_info("EFI_RNG_PROTOCOL unavailable, KASLR will be disabled\n");
+                               efi_nokaslr = true;
                        } else if (status != EFI_SUCCESS) {
-                               efi_err("efi_get_random_bytes() failed\n");
-                               return status;
+                               efi_err("efi_get_random_bytes() failed (0x%lx), KASLR will be disabled\n",
+                                       status);
+                               efi_nokaslr = true;
                        }
                } else {
                        efi_info("KASLR disabled on kernel command line\n");

diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index 11ecf3c4640ebce49d89a4349ffa05621e1f0d6d..368cd60000eec18ec3affe2a199a64631ac81fe4 100644 (file)
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -136,7 +136,7 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
        if (status)
                goto fdt_set_fail;
 
-       if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
+       if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && !efi_nokaslr) {
                efi_status_t efi_status;
 
                efi_status = efi_get_random_bytes(sizeof(fdt_val64),
@@ -145,8 +145,6 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
                        status = fdt_setprop_var(fdt, node, "kaslr-seed", fdt_val64);
                        if (status)
                                goto fdt_set_fail;
-               } else if (efi_status != EFI_NOT_FOUND) {
-                       return efi_status;
                }
        }