Commit d5553523 authored by Kees Cook's avatar Kees Cook Committed by Theodore Ts'o
Browse files

random: move rand_initialize() earlier 



Right now rand_initialize() is run as an early_initcall(), but it only
depends on timekeeping_init() (for mixing ktime_get_real() into the
pools). However, the call to boot_init_stack_canary() for stack canary
initialization runs earlier, which triggers a warning at boot:

random: get_random_bytes called from start_kernel+0x357/0x548 with crng_init=0

Instead, this moves rand_initialize() to after timekeeping_init(), and moves
canary initialization here as well.

Note that this warning may still remain for machines that do not have
UEFI RNG support (which initializes the RNG pools during setup_arch()),
or for x86 machines without RDRAND (or booting without "random.trust=on"
or CONFIG_RANDOM_TRUST_CPU=y).

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent eb9d1bf0

drivers/char/random.c

+2 −3
Original line number Diff line number Diff line
@@ -1783,7 +1783,7 @@ EXPORT_SYMBOL(get_random_bytes_arch); 
 * data into the pool to prepare it for use. The pool is not cleared

 * as that can only decrease the entropy in the pool.

 */

static void init_std_data(struct entropy_store *r)

static void __init init_std_data(struct entropy_store *r)

{

	int i;

	ktime_t now = ktime_get_real();
@@ -1810,7 +1810,7 @@ static void init_std_data(struct entropy_store *r) 
 * take care not to overwrite the precious per platform data

 * we were given.

 */

static int rand_initialize(void)

int __init rand_initialize(void)

{

	init_std_data(&input_pool);

	init_std_data(&blocking_pool);
@@ -1822,7 +1822,6 @@ static int rand_initialize(void) 
	}

	return 0;

}

early_initcall(rand_initialize);



#ifdef CONFIG_BLOCK

void rand_initialize_disk(struct gendisk *disk)

include/linux/random.h

+1 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy; 


extern void get_random_bytes(void *buf, int nbytes);

extern int wait_for_random_bytes(void);

extern int __init rand_initialize(void);

extern bool rng_is_initialized(void);

extern int add_random_ready_callback(struct random_ready_callback *rdy);

extern void del_random_ready_callback(struct random_ready_callback *rdy);

init/main.c

+14 −7
Original line number Diff line number Diff line
@@ -564,13 +564,6 @@ asmlinkage __visible void __init start_kernel(void) 
	page_address_init();

	pr_notice("%s", linux_banner);

	setup_arch(&command_line);

	/*

	 * Set up the the initial canary and entropy after arch

	 * and after adding latent and command line entropy.

	 */

	add_latent_entropy();

	add_device_randomness(command_line, strlen(command_line));

	boot_init_stack_canary();

	mm_init_cpumask(&init_mm);

	setup_command_line(command_line);

	setup_nr_cpu_ids();
@@ -655,6 +648,20 @@ asmlinkage __visible void __init start_kernel(void) 
	hrtimers_init();

	softirq_init();

	timekeeping_init();



	/*

	 * For best initial stack canary entropy, prepare it after:

	 * - setup_arch() for any UEFI RNG entropy and boot cmdline access

	 * - timekeeping_init() for ktime entropy used in rand_initialize()

	 * - rand_initialize() to get any arch-specific entropy like RDRAND

	 * - add_latent_entropy() to get any latent entropy

	 * - adding command line entropy

	 */

	rand_initialize();

	add_latent_entropy();

	add_device_randomness(command_line, strlen(command_line));

	boot_init_stack_canary();



	time_init();

	printk_safe_init();

	perf_event_init();

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