From: Jason A. Donenfeld Date: Wed, 16 Nov 2022 16:16:42 +0000 (+0100) Subject: efi: random: refresh non-volatile random seed when RNG is initialized X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=e7b813b32a42a3a6281a4fd9ae7700a0257c1d50;p=users%2Fjedix%2Flinux-maple.git efi: random: refresh non-volatile random seed when RNG is initialized EFI has a rather unique benefit that it has access to some limited non-volatile storage, where the kernel can store a random seed. Register a notification for when the RNG is initialized, and at that point, store a new random seed. Reviewed-by: Ard Biesheuvel Signed-off-by: Jason A. Donenfeld --- diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index a46df5d1d0942..16dae588f0e38 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -337,6 +337,24 @@ static void __init efi_debugfs_init(void) static inline void efi_debugfs_init(void) {} #endif +static void refresh_nv_rng_seed(struct work_struct *work) +{ + u8 seed[EFI_RANDOM_SEED_SIZE]; + + get_random_bytes(seed, sizeof(seed)); + efi.set_variable(L"RandomSeed", &LINUX_EFI_RANDOM_SEED_TABLE_GUID, + EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | + EFI_VARIABLE_RUNTIME_ACCESS, sizeof(seed), seed); + memzero_explicit(seed, sizeof(seed)); +} +static int refresh_nv_rng_seed_notification(struct notifier_block *nb, unsigned long action, void *data) +{ + static DECLARE_WORK(work, refresh_nv_rng_seed); + schedule_work(&work); + return NOTIFY_DONE; +} +static struct notifier_block refresh_nv_rng_seed_nb = { .notifier_call = refresh_nv_rng_seed_notification }; + /* * We register the efi subsystem with the firmware subsystem and the * efivars subsystem with the efi subsystem, if the system was booted with @@ -413,6 +431,7 @@ static int __init efisubsys_init(void) platform_device_register_simple("efi_secret", 0, NULL, 0); #endif + execute_with_initialized_rng(&refresh_nv_rng_seed_nb); return 0; err_remove_group: